#include<stdio.h>
int main()
{
    int a,b,c,d,res1,res2,counta,countc;

    scanf("%d %d %d %d",&a,&b,&c,&d);

    counta=0;
    countc=0;
    while(1)
    {
        res1=a-d;
        a=res1;
        counta++;
        if(res1<=0)
        {
        break;
        }
    }

    while(1)
    {
        res2=c-b;
        c=res2;
        countc++;
        if(res2<=0)
        {
        break;
        }
    }
    if(counta<countc)
    {
    printf("No\n");
    }
    else
    {
    printf("Yes\n");
    }

    return 0;
}
