#include <bits/stdc++.h>
#pragma comment(linker, "/STACK:500000000")
using namespace std;
int n, m, k, i, j, x, y, cnt;
vector<int> pi(3000);
char s[300005];
int gcd(int a, int b) {
  while (b) b ^= a ^= b ^= a %= b;
  return a;
}
map<int, int> mp;
int main() {
  scanf("%d %d\n", &n, &k);
  gets(s);
  for (i = 0; i < n; i++) {
    j = i;
    while (i < n && s[i] == '#') i++;
    if (i - j >= k) {
      printf("NO\n");
      return 0;
    }
  }
  printf("YES\n");
  return 0;
}
