#include <bits/stdc++.h>
using namespace std;
int T, n, m, k, t, l;
char str[300009];
int main() {
  int ncase = 0;
  while (scanf("%d%d", &n, &k) == 2) {
    scanf("%s", str);
    int maxv = 0;
    for (int i = 0; i < n; ++i) {
      int cnt = 0;
      while (i < n && str[i] == '#') {
        i++;
        cnt++;
      }
      maxv = max(maxv, cnt);
    }
    if (maxv < k)
      printf("YES\n");
    else
      printf("NO\n");
  }
  return 0;
}
