#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 a = 0;
  for (int i = 0; i < N - 1; ++i) {
    if (S[i] == '#' && S[i + 1] == '.') {
      a++;
    }
  }
  int b = 0;
  for (int i = N - 1; i >= 1; --i) {
    if (S[i - 1] == '#' && S[i] == '.') {
      b++;
    }
  }
  cout << min(a, b) << endl;
}
