#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k = 1e9 + 7, a = 0, b = 0;
  string s;
  cin >> n >> s;
  vector<int> black(n);
  vector<int> white(n);
  for (int i = 0; i < n; i++) {
    if (s[i] == '#')
      a++;
    else
      b++;
    black[i] = a;
    white[i] = b;
  }
  for (int i = 0; i < n; i++) k = min(k, black[i] + white[n - 1] - white[i]);
  cout << k;
}
