#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using Graph = vector<vector<int>>;
constexpr int INF = 1000000001;
constexpr ll mod = 1000000007;
constexpr double PI = 3.1415926535897932;
template <class T>
inline bool chmin(T& a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T>
inline bool chmax(T& a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
inline void init() {
  cin.tie(nullptr);
  cout.tie(nullptr);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(15);
}
int main() {
  init();
  int N;
  cin >> N;
  string s;
  cin >> s;
  int ans = INF;
  string a = s;
  int cnt = 0;
  for (int(i) = (0); (i) < (N - 1); ++(i)) {
    if (a[i] == '#' && a[i + 1] == '.') {
      ++cnt;
      a[i + 1] = '#';
    }
  }
  chmin(ans, cnt);
  a = s;
  cnt = 0;
  for (int(i) = (N)-1; (i) >= (1); --(i)) {
    if (a[i] == '.' && a[i - 1] == '#') {
      ++cnt;
      a[i - 1] = '.';
    }
  }
  chmin(ans, cnt);
  cout << ans << "\n";
  return 0;
}
