#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, jump, ex = 0;
  bool pos = true;
  string s;
  cin >> n >> jump;
  cin >> s;
  for (int i = 1; i < n; i++) {
    if (s[i] == '#') {
      ex++;
      if (ex == jump) {
        pos = false;
      }
    } else {
      ex = 0;
    }
  }
  if (pos == true) {
    cout << "YES";
  } else {
    cout << "NO";
  }
  cout << endl;
}
