#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  long long int n, k, count{0}, sum{0};
  cin >> n >> k;
  char ar[n];
  for (int i = 0; i < n; i++) {
    cin >> ar[i];
    if (count == k) {
      sum = 1;
      break;
    }
    if (ar[i] == '#')
      count += 1;
    else
      count = 0;
  }
  if (sum == 1)
    cout << "NO";
  else
    cout << "YES";
}
