#include <bits/stdc++.h>
using namespace std;
int main() {
  long n, k;
  while (cin >> n >> k) {
    string s;
    cin >> s;
    int has = 0, flag = 0;
    for (int i = 0; i < n; i++) {
      if (s[i] == '#')
        has++;
      else {
        if (has >= k) flag = 1;
        has = 0;
      }
    }
    if (has >= k) flag = 1;
    if (flag == 0)
      cout << "YES" << endl;
    else
      cout << "NO\n";
  }
  return 0;
}
