#include<iostream>
#include<vector>
#include<algorithm>
typedef long long ll;
using namespace std;


int main(void){
    ll l,r,m,k;
    cin>>l>>r>>m>>k;
    if(k==0){
        cout<<"Yes"<<endl;
        return 0;
    }
    if(m==1){
        cout<<"Yes"<<endl;
        return 0;
    }
    if(l==0){
        cout<<"Yes"<<endl;
        return 0;
    }
    if(r-l+1>=m){
        cout<<"Yes"<<endl;
        return 0;
    }
    if((l<=m)&&(m<=r)){
        cout<<"Yes"<<endl;
        return 0;
    }
    ll mi = k*l;
    ll ma = k*r;
    if((mi<=m)&&(m<=ma)){
        cout<<"Yes"<<endl;
        return 0;
    }
    ll x = mi/m;
    ll y = ma/m;
    if(ma%m!=0)y++;
    if(y-x>1)cout<<"Yes";
    else cout<<"No";
    
    return 0;
}