#include <bits/stdc++.h>
using namespace std;
void pl(long long a) { printf("%lld\n", a); }
void psl(long long a) { printf("%lld", a); }
void pll(long long a, long long b) { printf("%lld %lld\n", a, b); }
void plll(long long a, long long b, long long c) {
  printf("%lld %lld %lld\n", a, b, c);
}
void sss(string s) { cout << s, printf("\n"); }
long long string_to_ll(string s) {
  stringstream ss;
  ss << s;
  long long n;
  ss >> n;
  return n;
}
string ll_to_string(long long n) {
  stringstream ss;
  ss << n;
  string s;
  ss >> s;
  return s;
}
long long n, k, i, c, mx = 0;
string s;
int main() {
  scanf("%lld %lld", &n, &k);
  ;
  getchar();
  cin >> s;
  for (long long i = (long long)0; i < (long long)n; i++) {
    if (s[i] == '#')
      c++;
    else {
      mx = max(mx, c);
      c = 0;
      if (mx >= k) {
        sss("NO");
        return 0;
      }
    }
  }
  sss("YES");
  return 0;
}
