#include <stdio.h>
int main(){
    int a,b,c,d,count=0;
    scanf("%d%d%d%d",&a,&b,&c,&d);
    while(1){
        if(c>0){
            c=c-b;
            count++;
        }else break;
        if(a>0){
            a=a-d;
            count++;
        }else break;
    }
    if(count%2==0)
        printf("Yes");
    else
        printf("No");
}