/*
 * FileName:     B
 * CreatedDate:  2020-04-26 21:05:19 +0900
 * LastModified: 2020-04-26 21:10:57 +0900
 */

#include <stdio.h>

int main(void){
    int a,b,c,d;
    scanf("%d %d %d %d",&a,&b,&c,&d);
    int flag=0;
    for(int i=0;a>0||c>0;i++){
        if(i%2==0){
            c=c-b;
            flag=0;
        }
        else{
            a=a-d;
            flag=1;
        }
    }
    if(flag==0){
        printf("No\n");
        return 0;
    }
    printf("Yes\n");
    return 0;
}
