#include <bits/stdc++.h>
using namespace std;

using ll = long long;

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  
  ll l, r, m, k;
  cin >> l >> r >> m >> k;
  
  if (k == 0) {
    cout << "Yes\n";
    return 0;
  }
  
  ll minimum = k * l;
  ll maximum = k * r;
  
  if (maximum / m != minimum / m) cout << "Yes\n";
  else cout << "No\n";
}