#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k;
  cin >> n >> k;
  int flag = 0, cnt = 0;
  char ch;
  for (int i = 0; i < n; i++) {
    scanf("%c", &ch);
    if (ch == '.') cnt = 0;
    if (ch == '#') cnt++;
    if (cnt >= k) flag = 1;
  }
  if (flag)
    cout << "NO" << endl;
  else
    cout << "YES" << endl;
}
