#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)

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