#include <iostream>
using namespace std;
using ll = long long;

int main()
{
  ll l, r, m, k;
  cin >> l >> r >> m >> k;
  if ((l * k - 1 + m) / m != (r * k + m) / m)
    cout << "Yes\n";
  else
    cout << "No\n";
  return 0;
}