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