#include <bits/stdc++.h>
int main(void) {
  int i, n, cnt = 0;
  char stone[20000000];
  scanf("%d", &n);
  scanf("%s", stone);
  for (i = 0; i < n; i++) {
    if (stone[i] == '#' && stone[i + 1] == '.') {
      stone[i + 1] = '#';
      cnt += 1;
    }
  }
  printf("%d", cnt);
  return 0;
}
