#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<math.h>
typedef long long ll;

int hikaku(const void *n1,const void *n2)
{
    return -*(int*)n1+*(int*)n2;
}



int main()
{

    int l,r,m,k,ans;
    scanf("%d %d %d %d",&l,&r,&m,&k);
    
    ll s,b;
    s=l*k;
    b=r*k;

    if(s%m==0||b%m==0)
    {
        printf("Yes\n");
    }
    else
    {
        s=s/m;
        b=b/m;
        if(b-s>0)
        {
            printf("Yes\n");
        }
        else
        {
            printf("No\n");
        }
    }

    return 0;
}