#include <bits/stdc++.h>
using namespace std;
string s;
int d[1000002];
int main() {
  int i, j, k = 0, l = 0, m = 0, n, mx = 0;
  scanf("%d%d", &n, &k);
  cin >> s;
  for (i = 1; i <= n; i++) {
    if (s[i - 1] == '#') {
      l++;
    } else {
      mx = max(l, mx);
      l = 0;
    }
  }
  mx = max(l, mx);
  if (mx >= k) {
    cout << "NO";
    return 0;
  }
  cout << "YES";
}
