#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k;
  scanf("%d %d", &n, &k);
  string a;
  cin >> a;
  int ct = 0;
  for (int i = 0; i < n; i++) {
    if (a[i] == '#') {
      ct++;
      if (ct == k) {
        printf("NO");
        return 0;
      }
    } else {
      ct = 0;
    }
  }
  printf("YES");
  return 0;
}
