#include <bits/stdc++.h>
using namespace std;
char a[300005];
int main() {
  int n, k;
  while (scanf("%d%d", &n, &k) != EOF) {
    int MAX = -32765;
    int ans = 0;
    scanf("%s", a);
    for (int i = 0; i < n; i++) {
      if (a[i] == '#') ans++;
      if (ans > MAX) MAX = ans;
      if (a[i] == '.') ans = 0;
    }
    if (MAX >= k)
      printf("NO\n");
    else
      printf("YES\n");
  }
  return 0;
}
