#include <bits/stdc++.h>
using namespace std;
int main() {
  string s;
  int n, m, f = 0;
  cin >> n >> m;
  cin >> s;
  for (int i = 0; i < n; i++) {
    if (s[i] == '#')
      f++;
    else
      f = 0;
    if (f >= m) {
      cout << "NO";
      return 0;
    }
  }
  cout << "YES";
  return 0;
}
