1,a,I
2,a,I
3,a,I
4,a,I
5,a,I
1,a,II
2,a,II
3,a,II
4,a,II
5,a,II
1,a,III
2,a,III
3,a,III
4,a,III
5,a,III
1,b,I
2,b,I
3,b,I
4,b,I
5,b,I
1,b,II
2,b,II
3,b,II
4,b,II
5,b,II
1,b,III
2,b,III
3,b,III
4,b,III
5,b,III

and so on.