#include <bits/stdc++.h>
using namespace std;
using ll = long long;
constexpr ll atcoder_mod = 1e9 + 7;
template <typename T = int>
T in() {
  T x;
  cin >> x;
  return (x);
}
template <typename T = int, typename C = vector<T>>
C vecin(int N) {
  C x(N);
  for (int i = 0; i < (N); ++i) {
    x[i] = in<T>();
  }
  return move(x);
}
void vout() { cout << endl; }
template <typename Head, typename... Tail>
void vout(Head&& h, Tail&&... t) {
  cout << ' ' << h;
  vout(forward<Tail>(t)...);
}
void out() { cout << endl; }
template <typename Head, typename... Tail>
void out(Head&& h, Tail&&... t) {
  cout << h;
  vout(forward<Tail>(t)...);
}
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(10);
  int N = in();
  auto S = in<string>();
  auto T(S);
  int A = 0, B = 0;
  for (int i = 0; i < (N - 1); ++i) {
    if (S[i] == '#' && S[i + 1] == '.') {
      A++;
      S[i + 1] = '#';
    }
  }
  for (int i = 0; i < (N - 1); ++i) {
    if (T[N - 1 - i] == '.' && T[N - 2 - i] == '#') {
      B++;
      T[N - 2 - i] = '.';
    }
  }
  out(min(A, B));
  return 0;
}
