#include <bits/stdc++.h>
using namespace std;
char a[1000005];
int main() {
  int n, m, i, now = 0;
  scanf("%d %d", &n, &m);
  scanf("%s", a);
  for (i = 0; a[i] != '\0' && now < m; i++) {
    if (a[i] == '#')
      now++;
    else
      now = 0;
  }
  if (a[i] == 0)
    printf("YES\n");
  else
    printf("NO\n");
  return 0;
}
