N = int(input())
S = input()

def f(X):
    res = [0] * N
    for i, x in enumerate(X):
        if x == '.': res[i] = res[i-1] + 1 if i > 0 else 10 ** 18
    return res

F, B = f(S), f(S[::-1])[::-1]
M = max(min(F[i], B[i]) for i in range(N))
for i in range(N):
    if min(F[i], B[i]) == M:
        print(i + 1)
        break