#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k, i, x = 0;
  cin >> n >> k;
  char a;
  for (i = 0; i < n; i++) {
    cin >> a;
    if (a == '#') {
      x++;
      if (x == k) break;
    } else
      x = 0;
  }
  cout << (x == k ? "NO" : "YES");
  return 0;
}
