#include <bits/stdc++.h>
using namespace std;
template <typename P, typename Q>
ostream& operator<<(ostream& os, pair<P, Q> p) {
  os << "(" << p.first << "," << p.second << ")";
  return os;
}
template <typename P, typename Q>
istream& operator>>(istream& is, pair<P, Q>& p) {
  is >> p.first >> p.second;
  return is;
}
template <typename T>
ostream& operator<<(ostream& os, vector<T> v) {
  os << "(";
  for (auto& i : v) os << i << ",";
  os << ")";
  return os;
}
template <typename T>
istream& operator>>(istream& is, vector<T>& v) {
  for (auto& i : v) is >> i;
  return is;
}
template <typename T>
ostream& operator<<(ostream& os, set<T> s) {
  os << "#{";
  for (auto& i : s) os << i << ",";
  os << "}";
  return os;
}
template <typename K, typename V>
ostream& operator<<(ostream& os, map<K, V> m) {
  os << "{";
  for (auto& i : m) os << i << ",";
  os << "}";
  return os;
}
template <typename T>
inline T setmax(T& a, T b) {
  return a = std::max(a, b);
}
template <typename T>
inline T setmin(T& a, T b) {
  return a = std::min(a, b);
}
using lli = long long int;
using ull = unsigned long long;
using point = complex<double>;
using str = string;
template <typename T>
using vec = vector<T>;
constexpr array<int, 8> di({0, 1, -1, 0, 1, -1, 1, -1});
constexpr array<int, 8> dj({1, 0, 0, -1, 1, -1, -1, 1});
constexpr lli mod = 1e9 + 7;
int main(int argc, char* argv[]) {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.setf(ios_base::fixed);
  cout.precision(15);
  str s;
  int _;
  while (cin >> _ >> s) {
    int cnt = 0;
    for (int i = 1; i < s.size(); ++i) {
      if (s[i - 1] == '#' && s[i] == '.') {
        s[i] = '#';
        ++cnt;
      }
    }
    cout << cnt << endl;
  }
  return 0;
}
