#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k;
  string g;
  cin >> n >> k;
  cin >> g;
  int c = 0;
  n = g.size();
  for (int i = 0; i < n; i++) {
    if (g[i] != '#') {
      if (c >= k) {
        cout << "NO" << endl;
        return 0;
      }
      c = 0;
    } else
      c++;
  }
  if (g[n - 1] == '#') {
    cout << "NO" << endl;
    return 0;
  }
  cout << "YES" << endl;
  return 0;
}
