# -*- coding: utf-8 -*-

import sys

def input(): return sys.stdin.readline().strip()
def list2d(a, b, c): return [[c] * b for i in range(a)]
def list3d(a, b, c, d): return [[[d] * c for j in range(b)] for i in range(a)]
def ceil(x, y=1): return int(-(-x // y))
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
def Yes(): print('Yes')
def No(): print('No')
def YES(): print('YES')
def NO(): print('NO')
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
MOD = 10 ** 9 + 7

N=INT()
S=input()

S2=list(S)
cnt1=0
for i in range(1, N):
    if S2[i-1]=='#' and S2[i]=='.':
        S2[i]='#'
        cnt1+=1

S3=list(S)
cnt2=0
for i in range(N-1, 0, -1):
    if S3[i-1]=='#' and S3[i]=='.':
        S3[i-1]='.'
        cnt2+=1

print(min(cnt1, cnt2))
