#include <bits/stdc++.h>
using namespace std;
char s[3 * 100000 + 10];
int k, n;
int main() {
  cin >> n >> k;
  cin >> s;
  int con = 0;
  int flag = 0;
  for (int i = 0; i < n; i++) {
    if (s[i] == '#')
      con++;
    else
      con = 0;
    if (con == k) {
      flag = 1;
      break;
    }
  }
  if (s[n - 1] == '#') {
    cout << "NO" << endl;
    return 0;
  }
  if (flag)
    cout << "NO" << endl;
  else
    cout << "YES" << endl;
}
