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