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