#include <bits/stdc++.h>
const int INF = 2147483647;
const long long int MOD = 1000000007;
using namespace std;
using ll = long long;
using P = pair<int, int>;
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 main() {
  ll n;
  string s;
  cin >> n >> s;
  ll pos = 0;
  ll black = 0;
  while (pos < n && s[pos] != '#') {
    if (s[pos] == '#') black++;
    pos++;
  }
  ll b = pos;
  ll res = 0;
  while (pos < n) {
    if (s[pos] == '.') res++;
    if (s[pos] == '#') black++;
    pos++;
  }
  cout << min(black, res) << endl;
  return 0;
}
