#include <bits/stdc++.h>
using namespace std;
const int INF = 1e9;
long long gcd(long long x, long long y) {
  if (x < y) {
    long long temp = x;
    x = y;
    y = temp;
  }
  long long r = x % y;
  while (r != 0) {
    x = y;
    y = r;
    r = x % y;
  }
  return y;
}
int main() {
  int N;
  string S_1;
  cin >> N;
  cin >> S_1;
  int n;
  int cnt_1 = 0;
  int cnt_2 = 0;
  string S_2 = S_1;
  string S_1r = S_1;
  string S_2r = S_1;
  reverse(S_1r.begin(), S_1r.end());
  reverse(S_2r.begin(), S_2r.end());
  int cnt_1r = 0;
  int cnt_2r = 0;
  for (int i = 0; i < N - 1; i++) {
    if (S_1[i] == '#' && S_1[i + 1] == '.') {
      cnt_1++;
      S_1[i + 1] = '#';
    }
  }
  for (int i = 0; i < N - 1; i++) {
    if (S_1r[i] == '.' && S_1[i + 1] == '#') {
      cnt_1r++;
      S_1r[i] = '#';
    }
  }
  if (cnt_1 == 0) cnt_1 = cnt_1r;
  for (int i = 0; i < N - 1; i++) {
    if (S_2[i] == '#' && S_2[i + 1] == '.') {
      cnt_2++;
      S_2[i] = '.';
    }
  }
  for (int i = 0; i < N - 1; i++) {
    if (S_2r[i] == '.' && S_2[i + 1] == '#') {
      cnt_2r++;
      S_2r[i + 1] = '.';
    }
  }
  if (cnt_2 == 0) cnt_2 = cnt_2r;
  cout << min(cnt_1, cnt_2) << endl;
}
