#include <bits/stdc++.h>
using namespace std;
int NOD(int a, int b) {
  if (b == 0)
    return a;
  else
    return NOD(b, a % b);
}
int main() {
  int n, k;
  cin >> n >> k;
  vector<char> road(n);
  for (int i = 0; i < n; i++) cin >> road[i];
  int m = 0;
  int tmp = 0;
  for (int i = 0; i < n; i++) {
    if (road[i] == '#')
      tmp++;
    else {
      m = max(m, tmp);
      tmp = 0;
    }
  }
  if (m < k)
    cout << "YES";
  else
    cout << "NO";
  return 0;
}
