#include<stdio.h>
int main()
{
    int th,ts,ah,as,rem1,rem2;
    scanf("%d %d %d %d",&th,&ts,&ah,&as);
    while(1)
    {
        if(th>=as)
            th=th-as;


        if(ah>=ts)
            ah=ah-ts;
        if(th<=0||ah<=0)
            break;
    }
    th>ah?printf("Yes\n"):printf("No\n");
    return 0;

}
