#include <bits/stdc++.h>
using namespace std;
using ll = long long;
string char_to_string(char val) { return string(1, val); }
int char_to_int(char val) { return val - '0'; }
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;
}
int vector_finder(std::vector<ll> vec, int number) {
  auto itr = std::find(vec.begin(), vec.end(), number);
  size_t index = std::distance(vec.begin(), itr);
  if (index != vec.size()) {
    return 1;
  } else {
    return 0;
  }
}
int main() {
  int N;
  cin >> N;
  string S;
  cin >> S;
  int ans = 0;
  int a = 0;
  int b = 0;
  bool flag = false;
  for (int i = 0, i_len = (N); i < i_len; ++i) {
    if (flag == true && S[i] == '#') {
      ans += min(a, b);
      a = 0;
      b = 0;
    }
    if (S[i] == '#') {
      flag = false;
      a++;
    }
    if (S[i] == '.') {
      flag = true;
      b++;
    }
    if (i == N - 1) {
      ans += min(a, b);
    }
  }
  cout << ans << endl;
}
