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