i did the math for you the answer is 3 groups with 21 people in each groups
28+25=63
1 1 1 1
1 1 1 1
1 1 1 1. 21 first group
1 1 1 1
1 1 1 1
1
1 1 1 1
1 1 1 1. 21 second groups
1 1 1 1
1 1 1 1
1 1 1 1
1
1 1 1 1
1 1 1 1
1 1 1 1. 21 third groups
1 1 1 1
1 1 1 1
1
21+21+21=63
or u can 63÷3=21