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