from collections import defaultdict
from string import ascii_uppercase
import sys, bisect, math,string
stdin = sys.stdin
read_int = lambda : list(map(int,stdin.readline().split()))
read_str = lambda : stdin.readline().rstrip()

N = read_int()[0]
S = read_str()

def solve():
    ans = 0
    head_dot = 0
    tail_hash = N
    for i in range(N):
        if S[i] != ".":
            break
        head_dot += 1
    for i in range(N):
        if S[N - i -1] != "#":
            break
        tail_hash -= 1

    ans = min(S[head_dot:tail_hash+1].count("."), S[head_dot:tail_hash+1].count("#"))
    return ans

if __name__ == "__main__":
    print(solve())
