#include <bits/stdc++.h>
using namespace std;
int n, m, len;
int main() {
  cin >> n >> m;
  for (int i = 1; i <= n; i++) {
    char ch;
    cin >> ch;
    if (ch == '#')
      len++;
    else
      len = 0;
    if (len >= m) {
      puts("NO");
      return 0;
    }
  }
  puts("YES");
  return 0;
}
