#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using vll = vector<long long>;
using sll = set<long long>;
template <typename T>
T gcd(T a, T b) {
  return b ? gcd(b, a % b) : a;
}
template <typename T>
T lcm(T a, T b) {
  return a / gcd(a, b) * b;
}
template <typename T>
map<T, T> getPrimeFactor(T n) {
  map<T, T> res;
  for (T i = 2; i * i <= n; ++i) {
    while (n % i == 0) {
      res[i]++;
      n /= i;
    }
  }
  if (n != 1) res[n] = 1;
  return res;
}
template <typename T>
bool IsPrimeNumber(T num) {
  if (num <= 2)
    return true;
  else if (num % 2 == 0)
    return false;
  double sqrtNum = sqrt(num);
  for (int i = 3; i <= sqrtNum; i += 2) {
    if (num % i == 0) {
      return false;
    }
  }
  return true;
}
long long modinv(long long a, long long m) {
  long long b = m, u = 1, v = 0;
  while (b) {
    long long t = a / b;
    a -= t * b;
    swap(a, b);
    u -= t * v;
    swap(u, v);
  }
  u %= m;
  if (u < 0) u += m;
  return u;
}
int main() {
  ll N;
  string S;
  std::cin >> N >> S;
  bool flg = false;
  ll cnt_white = 0, cnt_black = 0;
  for (ll i = S.length() - 1; i >= 0; i--) {
    if (S[i] == '.') {
      flg = true;
    }
    if (flg) {
      if (S[i] == '.') {
        cnt_white++;
      } else {
        cnt_black++;
      }
    }
  }
  std::cout << min(cnt_black, cnt_white) << endl;
  return 0;
}
