#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k;
  int i;
  char ara[300005];
  cin >> n >> k;
  for (i = 0; i < n; i++) cin >> ara[i];
  int c = 0;
  for (i = 0; i < n; i++) {
    if (ara[i] == '#') {
      c++;
      if (c >= k) {
        cout << "NO" << endl;
        return 0;
      }
    } else
      c = 0;
  }
  cout << "YES" << endl;
  return 0;
}
