#include <bits/stdc++.h>
using namespace std;
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  int n;
  string s;
  vector<int> ans;
  int fb = -1;
  int cw = 0, cb = 0;
  cin >> n;
  cin >> s;
  vector<int> ss(n + 1);
  ss[0] = 0;
  for (int i = 0; i < n; i++) {
    ss[i + 1] = ss[i] + (s[i] == '#');
  }
  for (int i = 0; i < n; i++) {
    if (s[i] == '#') {
      const int lb = ss[i - 1] - ss[0];
      const int rb = ss[n] - ss[i];
      const int ln = i, rn = n - i;
      const int lw = ln - lb, rw = rn - rb;
      const int ww = lb + rb;
      const int wb = lb + rw;
      const int bb = lw + rw;
      ans.push_back(min(min(ww, wb), bb));
    }
  }
  if (ans.empty())
    cout << 0 << endl;
  else
    cout << *min_element(ans.begin(), ans.end());
  return 0;
}
