#include <bits/stdc++.h>
using namespace std;
typedef unsigned int UI;
typedef long int LI;
typedef unsigned long int ULI;
typedef long long int LL;
typedef unsigned long long int ULL;
const LL MOD = 1e9 + 7;
inline int scanInt() {
  int n = 0;
  char ch = getchar();
  int sign = 1;
  while (ch < '0' || ch > '9') {
    if (ch == '-') sign = -1;
    ch = getchar();
  }
  while (ch >= '0' && ch <= '9') {
    n = (n << 1) + (n << 3) + (int)(ch - '0');
    ch = getchar();
  }
  return n * sign;
}
inline LL scanLong() {
  LL n = 0;
  char ch = getchar();
  LL sign = 1;
  while (ch < '0' || ch > '9') {
    if (ch == '-') sign = -1;
    ch = getchar();
  }
  while (ch >= '0' && ch <= '9') {
    n = (n << 1) + (n << 3) + (LL)(ch - '0');
    ch = getchar();
  }
  return n * sign;
}
int main() {
  LL n = scanLong();
  ;
  string str;
  cin >> str;
  LL blacks = count(str.begin(), str.end(), '#'),
     whites = count(str.begin(), str.end(), '.');
  LL first_black = -1;
  if (blacks > 0) first_black = find(str.begin(), str.end(), '#') - str.begin();
  LL ans = 0;
  if (blacks > 0) ans = min(blacks, whites - first_black);
  printf("%lld ", ans);
  printf("\n");
}
