#include<stdio.h>
int main()
{
    int a,b,c,d,m,n,s1,s2;
    scanf("%d%d%d%d",&a,&b,&c,&d);
    m=c/b;
    n=a/d;
    s1=c-(b*m);
    s2=a-(d*n);
    if(s1<=0)
        printf("Yes\n");
    else if(s1>0)
        printf("No\n");
}