n回に一回だけ正を返す・一回だけ負を返す

n = 3
for i in range(10):
    print i, i%n/(n-1), ~i%-n/(n-1)/-1
==
0 0 1
1 0 1
2 1 0
3 0 1
4 0 1
5 1 0
6 0 1
7 0 1
8 1 0
9 0 1