#include <bits/stdc++.h>
using namespace std;
const int N = 112345;
bool used[N];
int ss[N];
int main() {
  int n, m, i, j;
  cin >> n >> m;
  string s;
  cin >> s;
  int cnt = 0;
  for (i = 0; i < n; i++) {
    if (s[i] == '#')
      cnt++;
    else
      cnt = 0;
    if (cnt >= m) {
      puts("NO");
      return 0;
    }
  }
  puts("YES");
}
