#include <bits/stdc++.h>
using namespace std;
int main() {
  char s[400000];
  int n, k, cnt = 0, ans = 0;
  scanf("%d%d", &n, &k);
  scanf("%s", &s);
  int len = strlen(s);
  for (int i = 0; i < len; i++) {
    if (s[i] == '#')
      cnt++;
    else {
      ans = max(ans, cnt);
      cnt = 0;
    }
  }
  if (ans >= k)
    printf("NO\n");
  else
    printf("YES\n");
}
