#include <bits/stdc++.h>
using namespace std;
int n, k, now, i;
char a[1100000];
bool flag;
int main() {
  scanf("%d%d", &n, &k);
  scanf("%s", a);
  flag = true;
  for (i = 0; i < n; i++) {
    if (a[i] == '.')
      now = 0;
    else
      now++;
    if (now >= k) flag = false;
  }
  printf(flag ? "YES\n" : "NO\n");
}
