#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k, prev = 0;
  string s;
  cin >> n >> k >> s;
  for (int i = 1; i < n; i++)
    if (s[i] == '.') {
      if (i - prev > k) {
        printf("NO");
        return 0;
      }
      prev = i;
    }
  printf("YES");
  return 0;
}
