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