#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k, i, cnt = 0;
  char s[400000];
  cin >> n >> k;
  cin >> s;
  for (i = 0; i < n; i++) {
    if (s[i] == '#')
      cnt++;
    else
      cnt = 0;
    if (cnt >= k) {
      cout << "NO" << endl;
      return 0;
    }
  }
  cout << "YES" << endl;
}
