a,b,c,s
0,1,2,3.0
1,2,3,6.0
2,3,4,9.0
3,4,5,12.0
4,5,6,15.0
5,6,7,18.0
6,7,8,21.0
7,8,9,24.0
8,9,10,27.0
9,10,11,30.0