#include <bits/stdc++.h>
using namespace std;
void solve() {
  long long int a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u,
      v, w, x, y, z;
  string ss;
  cin >> n >> m;
  cin >> ss;
  bool ans = false;
  c = 0;
  for (i = 0; i < ss.size(); i++) {
    if (ss[i] == '#')
      c++;
    else {
      if (c < m) {
        c = 0;
      } else {
        ans = true;
        break;
      }
    }
  }
  if (ans)
    cout << "NO" << endl;
  else
    cout << "YES" << endl;
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long int tc;
  solve();
  return 0;
}
