#include <bits/stdc++.h>
using namespace std;
int main() {
  long n, k;
  long d = 0, Max = 0;
  cin >> n >> k;
  vector<char> v(n);
  for (int i = 0; i < n; i++) {
    cin >> v[i];
    if (v[i] == '#') {
      d++;
      Max = max(Max, d);
    } else {
      d = 0;
    }
  }
  if (Max < k) {
    cout << "YES";
  } else {
    cout << "NO";
  }
}
