N = int(input())
S = list(input())
 
res = 0
for i in range(len(S)-1):
    if S[i] == '#' and S[i+1] == '.':
        if i+2 <= len(S)-1:
            if S[i+2] == '.':
                S[i] = '.'
                res += 1
                continue
        res += 1
        S[i+1] = '#'

print(res)