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