#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  int n, d;
  cin >> n >> d;
  string s;
  cin >> s;
  int count = 0;
  for (int k = 0; k < s.size(); k++) {
    count = 0;
    if (s[k] == '#') {
      count++;
      k++;
      while (s[k] == '#') {
        count++;
        k++;
      }
    }
    if (count >= d) {
      cout << "NO";
      return 0;
    }
  }
  cout << "YES";
  return 0;
}
