PLAYER PAGE

Personal

Kekana, N (Neo)

Chess SA id

1090116741

FIDE id

?

Date of birth

2009-07-31 (U18)

Gender

Male

Region

Tshwane (GTP)

Citizen

RSA

Titles

Chess SA registered

No

Last active game

2025-09-13

Personal details last changed

1900-01-01

Junior GPX Games

62.9

Junior GPX Points

1596.2

Item Main Standard Rapid Blitz
Rating 1760.6 1760.2 1219.8 1200
Raw rating 1699.7 1711 1219.8 1200
Weighted rating 1513 1514.4 1219.4 1200
Weighted performance 1760.6 1760.2 0 0
Floor 1199.7 1211 722.4 700
K-factor 28 28 36 36
Min/Max rating change allowed 81.4 80.1 161.2 165.8
Highest rating 1760.6
2025-09-30
1760.2
2025-09-30
1313.4
2022-10-01
1200
2018-10-01
Highest raw rating 1699.7
2025-09-30
1711
2025-09-30
1222.4
2024-02-01
1200
2024-02-01
Highest weighted rating 1513
2025-09-30
1514.4
2025-09-30
1222.4
2024-10-01
1200
2018-10-01
Highest weighted performance 1772.6
2025-09-01
1771.3
2025-09-01
1313.4
2022-10-01
1200
2024-02-01

Prediction
Item Main Standard Rapid Blitz
Rating change -0.6 -0.6 0 0
New rating 1759.9 1759.6 1219.8 1200
Analysis
Rating 1760.6 1760.2 1219.8 1200
Raw rating 1699.7 1711 1219.8 1200
Weighted rating 1513 1514.4 1219.4
Weighted performance 1760.6 1760.2 0
K-factor 28 28 36 36
Floor 1199.7 1211 722.4 700
Max/Min rating change allowed 81.4 80.1 161.2 165.8
Games 0 0 0 0
Score 0 0 0 0
Expected score 0 0 0 0
Score-Expected 0 0 0 0
Temp raw +/- 0 0 0 0
Final raw +/- 0 0 0 0
New raw rating 1699.7 1711 1219.8 1200
New weighted rating 1531.6 1534 1219.4 1200
New weighted performance 1759.9 1759.6 0 0
Temp new rating 1759.9 1759.6 1219.8 1200
Temp new rating +/- -0.6 -0.6 0 0
Final new rating +/- -0.6 -0.6 0 0
New rating 1759.9 1759.6 1219.8 1200
New K-factor 28 28 36 36
New floor 1199.7 1211 722.4 700

Item Main Standard Rapid Blitz
0 0 0 0
55 55 0 0
91 86 5 0
77 77 0 0
37 32 5 0
0 0 0 0
History 270 260 10 0

Games since
Main
151
Standard
146
Rapid
5
Blitz
0
Gender Male
Age group U18
Region Tshwane (GTP)
Province Gauteng (GT)
Main
RSA Province Region
Overall 202 85 31
Male 191 80 30
U18 22 11 6
U18 Male 22 11 6
Standard
RSA Province Region
Overall 206 88 31
Male 195 83 30
U18 23 12 7
U18 Male 23 12 7
Rapid
RSA Province Region
Overall -1 -1 -1
Male -1 -1 -1
U18 -1 -1 -1
U18 Male -1 -1 -1
Blitz
RSA Province Region
Overall -1 -1 -1
Male -1 -1 -1
U18 -1 -1 -1
U18 Male -1 -1 -1

Games Score % Dp AvgOpp Performance
Main 0 0 0 0 0 0
Standard 0 0 0 0 0 0
Rapid 0 0 0 0 0 0
Blitz 0 0 0 0 0 0
Games Score % Dp AvgOpp Performance
Main 55 40.5 73.64 200.9 1495 1695.9
Standard 55 40.5 73.64 200.9 1495 1695.9
Rapid 0 0 0 0 0 0
Blitz 0 0 0 0 0 0
History
Games Score % Dp AvgOpp Performance
Main 270 148 54.81 40.9 1344.7 1385.7
Standard 260 143 55 42.5 1342.8 1385.3
Rapid 10 5 50 0 1395.9 1395.9
Blitz 0 0 0 0 0 0

Date Main Standard Rapid Blitz
2025-09-30 1699.7 1711 1219.8 1200
2025-09-01 1697.9 1708.5 1219.8 1200
2025-08-01 1624.4 1624.2 1219.8 1200
2025-07-01 1551.7 1552.3 1219.8 1200
2025-06-01 1551.7 1552.3 1219.8 1200
2025-05-01 1551.2 1555.5 1219.8 1200
2025-04-01 1523.6 1526.6 1219.8 1200
2025-03-01 1523.6 1526.6 1219.8 1200
2025-02-01 1402.7 1399.2 1219.4 1200
2025-01-01 1370.5 1372.9 1212.3 1200
2024-12-01 1370.5 1372.9 1212.3 1200
2024-11-01 1370.5 1372.9 1212.3 1200
2024-10-01 1395.3 1387.9 1222.4 1200
2024-09-01 1424.8 1422.8 1222.4 1200
2024-08-01 1441.2 1441.4 1222.4 1200
2024-07-01 1448.6 1446.5 1222.4 1200
2024-06-01 1549.4 1547.6 1222.4 1200
2024-08-01 1519.8 1514.9 1222.4 1200
2024-04-01 1419.7 1410.2 1222.4 1200
2024-03-01 1375.4 1369.4 1222.4 1200
2024-02-01 1393.7 1387 1222.4 1200
2024-01-01 1338.4 1327.8 1222.4 1200
2023-12-01 1338.4 1327.8 1222.4 1200
2023-11-01 1338.4 1327.8 1222.4 1200

Comming soon.

Tournaments

No tournaments found.
# Tournament Start End Type Host Rounds Games Score Cfr Analysis
# Tournament Start End Type Host Rounds Games Score Cfr Analysis
1 Tshwane Chess Club Clash 2025 (Open) 2025-09-13 2025-09-13 Standard Tshwane (GTP) 5 5 3 Yes Analysis
2 2025 Midstream Open Chess Tournament (B) 2025-08-25 2025-08-25 Standard Tshwane (GTP) 5 5 4.5 Yes Analysis
3 2025 Tshwane North District CLOSED Team Championships (D3) (U17 Open) 2025-08-16 2025-08-16 Standard Tshwane (GTP) 5 5 4 Yes Analysis
4 2025 Etienne Lewis Closed Chess Tournament (U18) 2025-08-08 2025-08-10 Standard Tshwane (GTP) 7 6 5 Yes Analysis
5 2025 Wynie Robbertse Chess Tournament (B) 2025-07-19 2025-07-19 Standard Tshwane (GTP) 5 5 4 Yes Analysis
6 2025 Tshwane North School District CLOSED Individual Chess Championship (U18 Open) 2025-05-24 2025-05-24 Standard Tshwane (GTP) 5 5 3 Yes Analysis
7 Moja Chess Extravaganza 2025 (C) 2025-04-26 2025-05-01 Standard Johannesburg Metro (GJM) 9 9 6 Yes Analysis
8 2025 Mid Gauteng Open Chess Tournament (B) 2025-04-12 2025-04-12 Standard Tshwane (GTP) 5 5 2.5 Yes Analysis
9 2025 KSNG Open (C) 2025-02-22 2025-02-22 Standard Tshwane (GTP) 5 5 4 Yes Analysis
10 2025 Blou Bul Open Chess Tournament (C) 2025-02-08 2025-02-08 Standard Tshwane (GTP) 5 5 4.5 Yes Analysis
Last 500 tournaments since 01 January 2018
# Tournament Start End Type Host Rounds Games Score Cfr Analysis
1 Tshwane Chess Club Clash 2025 (Open) 2025-09-13 2025-09-13 Standard Tshwane (GTP) 5 5 3 Yes Analysis
2 2025 Midstream Open Chess Tournament (B) 2025-08-25 2025-08-25 Standard Tshwane (GTP) 5 5 4.5 Yes Analysis
3 2025 Tshwane North District CLOSED Team Championships (D3) (U17 Open) 2025-08-16 2025-08-16 Standard Tshwane (GTP) 5 5 4 Yes Analysis
4 2025 Etienne Lewis Closed Chess Tournament (U18) 2025-08-08 2025-08-10 Standard Tshwane (GTP) 7 6 5 Yes Analysis
5 2025 Wynie Robbertse Chess Tournament (B) 2025-07-19 2025-07-19 Standard Tshwane (GTP) 5 5 4 Yes Analysis
6 2025 Tshwane North School District CLOSED Individual Chess Championship (U18 Open) 2025-05-24 2025-05-24 Standard Tshwane (GTP) 5 5 3 Yes Analysis
7 Moja Chess Extravaganza 2025 (C) 2025-04-26 2025-05-01 Standard Johannesburg Metro (GJM) 9 9 6 Yes Analysis
8 2025 Mid Gauteng Open Chess Tournament (B) 2025-04-12 2025-04-12 Standard Tshwane (GTP) 5 5 2.5 Yes Analysis
9 2025 KSNG Open (C) 2025-02-22 2025-02-22 Standard Tshwane (GTP) 5 5 4 Yes Analysis
10 2025 Blou Bul Open Chess Tournament (C) 2025-02-08 2025-02-08 Standard Tshwane (GTP) 5 5 4.5 Yes Analysis
11 2024 Tshwane Chess Club Clash (Open) 2024-10-12 2024-10-12 Standard Tshwane (GTP) 5 5 2.5 Yes Analysis
12 Gauteng Top Schools 2024 (U17 Open) 2024-10-05 2024-10-05 Rapid Ekurhuleni (GE) 5 5 1.5 Yes Analysis
13 2024 Curro Hazeldean High Open Chess Tournament (B) 2024-09-07 2024-09-07 Standard Tshwane (GTP) 5 4 2 Yes Analysis
14 Gauteng Schools Individuals Finals 2024 (U15 Boys) 2024-08-17 2024-08-17 Standard Ekurhuleni (GE) 5 5 3 Yes Analysis
15 2024 Alekhine Open Chess Tournament (A) 2024-08-09 2024-08-10 Standard Tshwane (GTP) 5 5 2 Yes Analysis
16 2024 Tshwane North School District Team League Finals (U17) 2024-08-03 2024-08-03 Standard Tshwane (GTP) 5 5 2 Yes Analysis
17 2024 Midstream College Open Chess Tournament (A) 2024-07-20 2024-07-20 Standard Tshwane (GTP) 5 5 1 Yes Analysis
18 2024 Prestige College Open Chess Tournament (B) 2024-07-06 2024-07-06 Standard Tshwane (GTP) 5 5 2 Yes Analysis
19 2024 Elise Steenkamp Open Chess Tournament (Kings) 2024-06-15 2024-06-17 Standard Tshwane (GTP) 7 7 2 Yes Analysis
20 2024 Johannes Mabusela's 40th Birthday Chess Tournament F Section (C) 2024-06-01 2024-06-01 Standard Tshwane (GTP) 5 5 1.5 Yes Analysis
21 2024 Tshwane North School District CLOSED Individual Champioships (U15 Boys) 2024-05-11 2024-05-11 Standard Tshwane (GTP) 5 5 4 Yes Analysis
22 2024 Silver Lakes Open Chess Tournament (D1) 2024-04-21 2024-04-21 Standard Tshwane (GTP) 5 5 3 Yes Analysis
23 2024 Milos Ristic Open Chess Tournament (U16) 2024-04-27 2024-04-27 Standard Tshwane (GTP) 5 5 4 Yes Analysis
24 2024 KSNG CHess Academy Open Tournament (D1) 2024-04-06 2024-04-06 Standard Tshwane (GTP) 5 5 4 Yes Analysis
25 2024 Lubowski Open Chess Tournament (D1) 2024-03-23 2024-03-24 Standard Tshwane (GTP) 5 5 4 Yes Analysis
26 2024 Chris Greyling Open Chess Tournament (D3) 2024-03-16 2024-03-16 Standard Tshwane (GTP) 5 5 3 Yes Analysis
27 2024 Piet Robbertse Open Chess Tournament (C) 2024-02-03 2024-02-04 Standard Tshwane (GTP) 5 5 2.5 Yes Analysis
28 2024 Gauteng Inter-Region Chess Championship (U16C) 2024-01-13 2024-01-14 Standard Tshwane (GTP) 5 5 5 Yes Analysis
29 2023 Gauteng Noord (C) 2023-10-14 2023-10-15 Standard Tshwane (GTP) 5 5 2 Yes Analysis
30 2023 Gauteng Top Schools (U15 Mixed) 2023-08-19 2023-08-19 Standard West Rand (GWR) 5 5 1 Yes Analysis
31 2023 Tshwane North School District CLOSED League Championships (D3) 2023-08-12 2023-08-12 Standard Tshwane (GTP) 5 5 3 Yes Analysis
32 2023 Etienne Lewis Closed Tournament (U16) 2023-08-25 2023-08-27 Standard Tshwane (GTP) 7 7 3 Yes Analysis
33 Wynie Robbertse Open Tournament 2023 (C) 2023-06-03 2023-06-03 Standard Tshwane (GTP) 5 4 3 Yes Analysis
34 2023 Elize Steenkamp Open Tournament (C) 2023-06-16 2023-06-17 Standard Tshwane (GTP) 6 6 5 Yes Analysis
35 2023 Tshwane North School District CLOSED Individual Championships (D3) 2023-05-13 2023-05-13 Standard Tshwane (GTP) 5 5 4 Yes Analysis
36 2023 Mid Gauteng Open Tournament (C) 2023-05-06 2023-05-06 Standard Tshwane (GTP) 5 5 3 Yes Analysis
37 Gauteng Schools Individual Finals 2023 (U15 Boys) 2023-05-27 2023-05-27 Standard Ekurhuleni (GE) 5 5 3 Yes Analysis
38 Silver Lakes Open Chess Tournament (C) 2023-04-15 2023-04-15 Standard Tshwane (GTP) 5 5 2 Yes Analysis
39 2023 Milos Ristic Open Tournament (C) 2023-04-27 2023-04-27 Standard Tshwane (GTP) 5 5 2.5 Yes Analysis
40 Chris Greyling Open Tournament 2023 (C) 2023-03-21 2023-03-21 Standard Tshwane (GTP) 5 5 2 Yes Analysis
41 2023 Afrikaans Hoër Seunskool Open Chess Tournament (C) 2023-03-04 2023-03-04 Standard Tshwane (GTP) 5 5 2.5 Yes Analysis
42 2023 Piet Robbertse Fide Rated Open Chess Tournament (C) 2023-02-04 2023-02-05 Standard Tshwane (GTP) 5 5 1.5 Yes Analysis
43 2023 Tshwane Chess Open Registration Tournament (C2) 2023-01-28 2023-01-28 Standard Tshwane (GTP) 5 5 3 Yes Analysis
44 2022 Wynie Robbertse Open (U14) 2022-10-08 2022-10-08 Standard Tshwane (GTP) 5 5 3 Yes Analysis
45 2022 Gauteng North Chess Open (D) 2022-10-15 2022-10-16 Standard Tshwane (GTP) 5 5 3 Yes Analysis
46 OR Tambo Soncini Finals 2022 (Boys) 2022-10-29 2022-10-29 Rapid Ekurhuleni (GE) 5 5 3.5 Yes Analysis
47 2022 Etienne Lewis (U14 Open) 2022-09-02 2022-09-04 Standard Tshwane (GTP) 7 7 1.5 Yes Analysis
48 2022 Alekhine Open (D) 2022-08-13 2022-08-14 Standard Tshwane (GTP) 5 5 2 Yes Analysis
49 2022 Jacaranda Round Robin (I) 2022-07-30 2022-07-30 Standard Tshwane (GTP) 5 5 0 Yes Analysis
50 2022 Blou Bul Open (D) 2022-06-25 2022-06-26 Standard Tshwane (GTP) 5 5 1 Yes Analysis
51 2020 Blou Bul (C) 2020-02-15 2020-02-15 Standard Tshwane (GTP) 5 5 1 Yes Analysis
52 2019 D3 Team League (U11) 2019-07-20 2019-07-20 Standard Tshwane (GTP) 5 5 3 Yes Analysis

Top 3 Streaks

# Games Start End
1 11 Tournament
2025 Tshwane North District CLOSED Team Championships (D3)
Tournament
Tshwane Chess Club Clash 2025
date
2025-08-16
rnd
2
type
Standard
result
1
date
2025-09-13
rnd
2
type
Standard
result
1
Opponent
Wolfaardt, J (John Eduan)
Opponent
Schutte, R (Rico)
2 11 Tournament
2024 Lubowski Open Chess Tournament
Tournament
2024 Silver Lakes Open Chess Tournament
date
2024-03-23
rnd
3
type
Standard
result
1
date
2024-04-21
rnd
3
type
Standard
result
1
Opponent
Nkwadi, K (Karabo)
Opponent
Janse Van Rensburg, G (Gerrit)
3 10 Tournament
2024 Milos Ristic Open Chess Tournament
Tournament
2024 Johannes Mabusela's 40th Birthday Chess Tournament F Section
date
2024-04-27
rnd
3
type
Standard
result
1
date
2024-06-01
rnd
2
type
Standard
result
1
Opponent
Adamson, A (Amani)
Opponent
Nkabinde, N (Nkazimulo)
# Games Start End
1 11 Tournament
2025 Tshwane North District CLOSED Team Championships (D3)
Tournament
Tshwane Chess Club Clash 2025
date
2025-08-16
rnd
2
type
Standard
result
1
date
2025-09-13
rnd
2
type
Standard
result
1
Opponent
Wolfaardt, J (John Eduan)
Opponent
Schutte, R (Rico)
2 11 Tournament
2024 Lubowski Open Chess Tournament
Tournament
2024 Silver Lakes Open Chess Tournament
date
2024-03-23
rnd
3
type
Standard
result
1
date
2024-04-21
rnd
3
type
Standard
result
1
Opponent
Nkwadi, K (Karabo)
Opponent
Janse Van Rensburg, G (Gerrit)
3 10 Tournament
2024 Milos Ristic Open Chess Tournament
Tournament
2024 Johannes Mabusela's 40th Birthday Chess Tournament F Section
date
2024-04-27
rnd
3
type
Standard
result
1
date
2024-06-01
rnd
2
type
Standard
result
1
Opponent
Adamson, A (Amani)
Opponent
Nkabinde, N (Nkazimulo)
# Games Start End
1 2 Tournament
Gauteng Top Schools 2024
Tournament
Gauteng Top Schools 2024
date
2024-10-05
rnd
3
type
Rapid
result
1
date
2024-10-05
rnd
4
type
Rapid
result
0.5
Opponent
Tlhapane, O (Oatlegile Tshiamo)
Opponent
Lindokuhle, H (Hlatshwayo)
2 2 Tournament
OR Tambo Soncini Finals 2022
Tournament
OR Tambo Soncini Finals 2022
date
2022-10-29
rnd
4
type
Rapid
result
1
date
2022-10-29
rnd
5
type
Rapid
result
1
Opponent
Van Dalen, JJP (Jan)
Opponent
Perry-Fisher, IE (Iain Eric)
3 2 Tournament
OR Tambo Soncini Finals 2022
Tournament
OR Tambo Soncini Finals 2022
date
2022-10-29
rnd
1
type
Rapid
result
1
date
2022-10-29
rnd
2
type
Rapid
result
0.5
Opponent
Sephula, T (Tshepo)
Opponent
Moultrey, V (Valentino)
No games found.
# Games Start End
# Games Start End
1 6 Tournament
2025 Tshwane North District CLOSED Team Championships (D3)
Tournament
2025 Midstream Open Chess Tournament
date
2025-08-16
rnd
2
type
Standard
result
1
date
2025-08-25
rnd
2
type
Standard
result
1
Opponent
Wolfaardt, J (John Eduan)
Opponent
Rust, C (Christoph)
2 6 Tournament
2025 Tshwane North School District CLOSED Individual Chess Championship
Tournament
2025 Wynie Robbertse Chess Tournament
date
2025-05-24
rnd
3
type
Standard
result
1
date
2025-07-19
rnd
3
type
Standard
result
1
Opponent
Moshobane, K (Kutlwano)
Opponent
Van Zyl, A (Albertus Petrus)
3 6 Tournament
2024 Lubowski Open Chess Tournament
Tournament
2024 KSNG CHess Academy Open Tournament
date
2024-03-23
rnd
3
type
Standard
result
1
date
2024-04-06
rnd
3
type
Standard
result
1
Opponent
Nkwadi, K (Karabo)
Opponent
Reddy, KS (Kashen Shivaan)
# Games Start End
1 6 Tournament
2025 Tshwane North District CLOSED Team Championships (D3)
Tournament
2025 Midstream Open Chess Tournament
date
2025-08-16
rnd
2
type
Standard
result
1
date
2025-08-25
rnd
2
type
Standard
result
1
Opponent
Wolfaardt, J (John Eduan)
Opponent
Rust, C (Christoph)
2 6 Tournament
2025 Tshwane North School District CLOSED Individual Chess Championship
Tournament
2025 Wynie Robbertse Chess Tournament
date
2025-05-24
rnd
3
type
Standard
result
1
date
2025-07-19
rnd
3
type
Standard
result
1
Opponent
Moshobane, K (Kutlwano)
Opponent
Van Zyl, A (Albertus Petrus)
3 6 Tournament
2024 Lubowski Open Chess Tournament
Tournament
2024 KSNG CHess Academy Open Tournament
date
2024-03-23
rnd
3
type
Standard
result
1
date
2024-04-06
rnd
3
type
Standard
result
1
Opponent
Nkwadi, K (Karabo)
Opponent
Reddy, KS (Kashen Shivaan)
# Games Start End
1 2 Tournament
OR Tambo Soncini Finals 2022
Tournament
OR Tambo Soncini Finals 2022
date
2022-10-29
rnd
4
type
Rapid
result
1
date
2022-10-29
rnd
5
type
Rapid
result
1
Opponent
Van Dalen, JJP (Jan)
Opponent
Perry-Fisher, IE (Iain Eric)
2 1 Tournament
Gauteng Top Schools 2024
Tournament
Gauteng Top Schools 2024
date
2024-10-05
rnd
3
type
Rapid
result
1
date
2024-10-05
rnd
3
type
Rapid
result
1
Opponent
Tlhapane, O (Oatlegile Tshiamo)
Opponent
Tlhapane, O (Oatlegile Tshiamo)
3 1 Tournament
OR Tambo Soncini Finals 2022
Tournament
OR Tambo Soncini Finals 2022
date
2022-10-29
rnd
1
type
Rapid
result
1
date
2022-10-29
rnd
1
type
Rapid
result
1
Opponent
Sephula, T (Tshepo)
Opponent
Sephula, T (Tshepo)
No games found.
# Games Start End

Top 10 opponents most often played

# Opponent Main Standard Rapid Blitz
Gms Score Dp Gms Score Dp Gms Score Dp Gms Score Dp
Aor Prat Aor Prat Aor Prat Aor Prat
1 Mahlangu ,NP (Nkosinathi Phillip) 5 4.5 340 5 4.5 340 0 0 0 0 0 0
1308.9 1648.9 1295.5 1648.9 0 0 0 0
2 Mdluli ,S (Siyabonga) 4 0 -425 4 0 -425 0 0 0 0 0 0
1610.3 1185.3 1617.3 1185.3 0 0 0 0
3 Seitei ,N (Neo) 4 4 425 4 4 425 0 0 0 0 0 0
1220.6 1645.6 1201.8 1645.6 0 0 0 0
4 Mathe ,T (Thabang) 4 3 212.5 4 3 212.5 0 0 0 0 0 0
1410.1 1622.6 1408.2 1622.6 0 0 0 0
5 Msimango ,M (Moremi) 4 1.5 -106.2 4 1.5 -106.2 0 0 0 0 0 0
1483.8 1377.5 1486.6 1377.5 0 0 0 0
6 Nkwadi ,K (Karabo) 4 2.5 106.2 4 2.5 106.2 0 0 0 0 0 0
1230.3 1336.5 1222.8 1336.5 0 0 0 0
7 De Jager ,J (Jandre) 3 1 -141.7 3 1 -141.7 0 0 0 0 0 0
1247 1105.4 1241.2 1105.4 0 0 0 0
8 Buchner ,E (Emil) 3 1 -141.7 3 1 -141.7 0 0 0 0 0 0
1161.1 1019.4 1146.7 1019.4 0 0 0 0
9 Reddy ,KS (Kashen Shivaan) 3 2 141.7 3 2 141.7 0 0 0 0 0 0
1246.6 1388.3 1235.3 1388.3 0 0 0 0
10 Du Toit ,SJM (Stephanus (Matteo) Johannes Matheus) 3 0.5 -283.3 3 0.5 -283.3 0 0 0 0 0 0
1507 1223.7 1508.3 1223.7 0 0 0 0

Norms

No norms achieved.
# Norm Tournament Start End Rounds Games Score Details
© Chess South Africa