import numpy as np
n=int(input())
s=[a for a in input()]
s=[a.replace('.','0') for a in s]
s=[a.replace('#','1') for a in s]
s=[int(a) for a in s]
p=[i for i, x in enumerate(s) if x == 1]
s = np.array(s)
cnt = np.sum(s)
for i in p:
    s[-1 * (n-i):] = 1 - s[-1 * (n-i):]
    _cnt = np.sum(s)
    if cnt > _cnt:
        cnt =_cnt
print(cnt)