#include <bits/stdc++.h>
using namespace std;
using ll = long long int;
using ull = unsigned long long int;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
int dx[] = {1, 0, -1, 0, 1, -1, 1, -1};
int dy[] = {0, 1, 0, -1, 1, 1, -1, -1};
const int INT_INF = (int)(2e9);
const ll LL_INF = (ll)(2e18);
inline void fast_io() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
};
template <typename T, typename S>
inline ostream& operator<<(ostream& os, const pair<T, S> p) {
  cout << "[" << p.first << ";" << p.second << "]";
  return os;
}
template <typename T, typename S>
inline ostream& operator<<(ostream& os, const map<T, S> p) {
  for (auto el : p) cout << "[" << el.first << ";" << el.second << "]";
  return os;
}
template <typename T>
inline ostream& operator<<(ostream& os, const vector<T>& v) {
  for (auto el : v) cout << el << " ";
  return os;
}
template <typename T>
inline ostream& operator<<(ostream& os, const deque<T>& v) {
  for (auto el : v) cout << el << " ";
  return os;
}
template <typename T>
inline ostream& operator<<(ostream& os, const set<T>& v) {
  for (auto el : v) cout << el << " ";
  return os;
}
template <typename T>
inline vector<T> fetch_vec(int sz) {
  vector<T> ret(sz);
  for (auto& elem : ret) cin >> elem;
  return ret;
}
int N;
string S;
void input() {
  fast_io();
  cin >> N >> S;
}
int solve() {
  ll ans = 0;
  string T = S;
  for (int i = 0; i < N - 1; i++) {
    if (S[i] == '#' && S[i + 1] == '.') {
      ans++;
      S[i + 1] = '#';
    }
  }
  ll ans_rev = 0;
  for (int i = N - 1; i > 0; i--) {
    if (T[i - 1] == '#' && T[i] == '.') {
      ans_rev++;
      T[i - 1] = '.';
    }
  }
  cout << min({ans, ans_rev}) << endl;
  return 0;
}
int main() {
  input();
  solve();
  return 0;
}
