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

int main()
{
	ll l,r,m,k;
	cin >> l >> r >> m >> k;
	ll L = l*k;
	ll R = r*k;
	if(k==0)
	{
		cout<<"Yes"<<endl;
		return 0;
	}

	if(R-L>m)
	{
		cout<<"Yes"<<endl;
	}
	else
	{
		R %= m;
		L %= m;
		if(R<L)
		{
			cout<<"Yes"<<endl;
		}
		else
		{
			cout<<"No"<<endl;
		}
		
	}
	
}