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