#include <bits/stdc++.h>
using namespace std;
template <typename T>
ostream& operator<<(ostream& os, const vector<T>& vec) {
  os << "[";
  for (int i = 0; i < vec.size(); i++) {
    os << vec[i] << ",";
  }
  os << "]";
  return os;
}
template <typename T>
T input() {
  T t;
  cin >> t;
  return t;
}
template <typename T>
vector<T> input(const int N) {
  vector<T> v(N);
  for (int i = 0; i < static_cast<int>(N); i++) cin >> v[i];
  return v;
}
long long gcd(long long a, long long b) {
  if (b == 0) {
    return a;
  }
  return gcd(b, a % b);
}
long long lcm(long long a, long long b) { return (a / gcd(a, b)) * b; }
long long mul(const long long& a, const long long& b, const long long& mod) {
  return ((a % mod) * (b % mod)) % mod;
}
long long power(const long long& x, const long long& y, const long long& mod) {
  if (y == 0) {
    return 1;
  } else if (y == 1) {
    return x % mod;
  } else {
    long long value = power(x, y / 2, mod);
    if (y % 2 == 0) {
      return mul(value, value, mod);
    } else {
      return mul(value, value, mod) * x % mod;
    }
  }
}
long long div(const long long& a, const long long& b, const long long& mod) {
  return mul(a, power(b, mod - 2, mod), mod);
}
map<long long, long long> factorials;
long long factorial(const long long& n, const long long& mod) {
  if (n == 0 || n == 1) {
    return 1;
  }
  if (factorials[n] != 0) {
    return factorials[n];
  }
  factorials[n] = n * factorial(n - 1, mod) % mod;
  return factorials[n] % mod;
}
long long combination(const long long& n, const long long& x,
                      const long long& mod) {
  long long numerator = 1;
  long long denominator = 1;
  for (int i = 0; i < static_cast<int>(x); i++) {
    numerator *= (n - i) % mod;
    numerator %= mod;
    denominator *= (i + 1) % mod;
    denominator %= mod;
  }
  return div(numerator, denominator, mod);
}
int main() {
  int N;
  string S;
  cin >> N >> S;
  int fromLeft = 0;
  char prevLeft = S[0];
  int fromRight = 0;
  char prevRight = S[S.size() - 1];
  int allBlack = 0;
  int allWhite = 0;
  for (int i = 0; i < S.size(); ++i) {
    char left = S[i];
    if (prevLeft != left) {
      if (prevLeft == '#') {
        fromLeft += 1;
      } else {
        prevLeft = left;
      }
    }
    char right = S[S.size() - i - 1];
    if (prevRight != right) {
      if (prevRight == '.') {
        fromRight += 1;
      } else {
        prevRight = right;
      }
    }
    if (left == '#') {
      allWhite += 1;
    } else {
      allBlack += 1;
    }
  }
  cout << min(allWhite, min(allBlack, min(fromLeft, fromRight))) << endl;
  return 0;
}
