#include <bits/stdc++.h>
using namespace std;
const long double PI = 4 * atan(1);
void solve() {
  long long int n, k;
  cin >> n >> k;
  string s;
  cin >> s;
  bool flag = true;
  int cnt = 0;
  for (int i = 0; i < n; i++) {
    if (s[i] == '.')
      cnt = 0;
    else
      cnt++;
    if (cnt == k) flag = false;
  }
  if (flag)
    cout << "YES" << endl;
  else
    cout << "NO" << endl;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(0);
  solve();
  return 0;
}
