#include <bits/stdc++.h>
using namespace std;
int main() {
  int rd, ju;
  cin >> rd >> ju;
  char c;
  int temp = 0;
  bool can = 1;
  for (int i = 0; i < rd; i++) {
    cin >> c;
    if (temp > ju - 1) can = 0;
    if (c == '#')
      temp++;
    else
      temp = 0;
  }
  if (can)
    cout << "YES";
  else
    cout << "NO";
  return 0;
}
