#include <bits/stdc++.h>
using namespace std;
using ll = long long;
template <typename T = ll>
using v = vector<T>;
template <typename T = ll>
using vv = v<v<T>>;
template <typename T = ll, typename U = ll>
using p = pair<T, U>;
template <typename T>
T chmin(T& a, T b) {
  return a = min(a, b);
}
template <typename T>
T chmax(T& a, T b) {
  return a = max(a, b);
}
const ll INF = (ll)1e9;
template <int MOD>
struct ModInt {
  using lint = long long;
  int val;
  ModInt(lint v = 0) : val(v % MOD) {
    if (val < 0) val += MOD;
  };
  ModInt operator+() const { return ModInt(val); }
  ModInt operator-() const { return ModInt(MOD - val); }
  ModInt inv() const { return this->pow(MOD - 2); }
  ModInt operator+(const ModInt& x) const { return ModInt(*this) += x; }
  ModInt operator-(const ModInt& x) const { return ModInt(*this) -= x; }
  ModInt operator*(const ModInt& x) const { return ModInt(*this) *= x; }
  ModInt operator/(const ModInt& x) const { return ModInt(*this) /= x; }
  ModInt pow(lint n) const {
    auto x = ModInt(1);
    auto b = *this;
    while (n > 0) {
      if (n & 1) x *= b;
      n >>= 1;
      b *= b;
    }
    return x;
  }
  ModInt& operator+=(const ModInt& x) {
    if ((val += x.val) >= MOD) val -= MOD;
    return *this;
  }
  ModInt& operator-=(const ModInt& x) {
    if ((val -= x.val) < 0) val += MOD;
    return *this;
  }
  ModInt& operator*=(const ModInt& x) {
    val = lint(val) * x.val % MOD;
    return *this;
  }
  ModInt& operator/=(const ModInt& x) { return *this *= x.inv(); }
  ModInt operator++(int) {
    auto t = *this;
    *this += 1;
    return t;
  }
  ModInt operator--(int) {
    auto t = *this;
    *this -= 1;
    return t;
  }
  ModInt operator<<(const int n) { return ModInt(*this) * ModInt(2).pow(n); }
  bool operator==(const ModInt& b) const { return val == b.val; }
  bool operator!=(const ModInt& b) const { return val != b.val; }
  friend std::istream& operator>>(std::istream& is, ModInt& x) noexcept {
    return is >> x.val;
  }
  friend std::ostream& operator<<(std::ostream& os, const ModInt& x) noexcept {
    return os << x.val;
  }
};
constexpr int MOD = 1e9 + 7;
using mint = ModInt<MOD>;
void c() {
  ll N;
  cin >> N;
  string S;
  cin >> S;
  ll cntB = count_if(S.begin(), S.end(), [](char c) { return c == '#'; });
  ll cntW = count_if(S.begin(), S.end(), [](char c) { return c == '.'; });
  ll ans = min(cntB, cntW);
  ll tmp = 0;
  v<> cnt;
  S.push_back('#');
  for (ll i = 0; i < (S.size()); i++) {
    if (S[i] == '#') cnt.push_back(i);
  }
  ll chk_ans = 0;
  for (ll i = 0; i < (cnt.size() - 1); i++) {
    chk_ans += cnt[i + 1] - cnt[i] - 1;
  }
  chmin(ans, chk_ans);
  cout << ans << endl;
}
int main() { c(); }
