21
1, 2, 6
1, 2, 7
1, 2, 8
1, 2, 9
1, 3, 10
1, 3, 11
1, 3, 12
1, 3, 13
1, 4, 14
1, 4, 15
1, 4, 16
1, 4, 17
1, 5, 18
1, 5, 19
1, 5, 20
1, 5, 21