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