- when n = 4,
I = 1 = 000 + 1, p = 000 = 0, ans = 0 + 2**3;
I = 2 = 001 + 1, p = 100 = 4, ans = 4 + 2**3;
I = 3 = 010 + 1, p = 010 = 2, ans = 2 + 2**3;
I = 4 = 011 + 1, p = 110 = 6, ans = 6 + 2**3;
... .
Answer: stdio.h takes only a quarter of the time (used by iostream).