/* -*- coding: utf-8 -*-
 *
 * 1048.cc:  No.1048 Zero (Advanced) - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

/* typedef */

typedef long long ll;

/* global variables */

/* subroutines */

/* main */

int main() {
  int l, r, m, k;
  scanf("%d%d%d%d", &l, &r, &m, &k);

  ll n0 = (ll)l * k, n1 = (ll)r * k;
  ll n = n1 / m * m;

  if (n0 <= n) puts("Yes");
  else puts("No");
  return 0;
}