#include <bits/stdc++.h>
int main(void) {
  int n, cnt1 = 0, cnt2 = 0, cnt3 = 0, f = 0;
  char s[2000000], sp[2000000];
  scanf("%d", &n);
  scanf("%s", &s);
  for (int i = 0; i < n; i++) sp[i] = s[i];
  for (int i = 0; i < n; i++) {
    if ((f == 0) && s[i] == '#') f = 1;
    if ((f == 1) && s[i] == '.') cnt1++;
  }
  f = 0;
  for (int i = n - 1; i >= 0; i--) {
    if ((f == 0) && s[i] == '.') f = 1;
    if ((f == 1) && s[i] == '#') cnt2++;
  }
  for (int i = 1; i < n - 1; i++) {
    if ((sp[i - 1] == sp[i + 1]) && (sp[i - 1] != sp[i])) {
      sp[i] = sp[i - 1];
      cnt3++;
    }
    if ((i == n - 2) && sp[i] == '#') {
      if (sp[i + 1] == '.') cnt3++;
    }
  }
  if (cnt1 < cnt2) {
    if (cnt1 < cnt3)
      printf("%d\n", cnt1);
    else
      printf("%d\n", cnt3);
  } else if (cnt2 < cnt3)
    printf("%d\n", cnt2);
  else
    printf("%d\n", cnt3);
  return 0;
}
