Dear S.K.

The formula you are looking for is:

Number of sets = (N - 3 + 2*(N MOD(3)) / 3, N = 1, 2, 3, .........

Examples: N = 5: number = (5 - 3 + 2*2) / 3 = 2
N = 100: number = (100 - 3 + 2*1) / 3 = 33

Hub Boreas