#include <bits/stdc++.h>
using namespace std;
int main(void) {
  int N;
  string S;
  cin >> N >> S;
  int cnt1 = 0;
  int cnt2 = 0;
  int now = 1;
  int flag1 = 0;
  int flag2 = 0;
  if (S[0] == '.') {
    flag1 = 1;
    now = 0;
  }
  for (int i = 0; i < N; i++) {
    if (S[i] == '#') {
      cnt2 += 1;
    }
    if (now == 1) {
      if (S[i] == '.' and flag1 != 1) {
        cnt1 += 1;
        flag2 = 1;
        now = 1 - now;
      }
    } else {
      if (S[i] == '#') {
        now = 1 - now;
        flag2 = 0;
      } else {
        if (flag2 == 1) {
          cnt1 += 1;
        }
      }
    }
  }
  int result = min(cnt1, cnt2);
  cout << result << endl;
  return 0;
}
