#include<bits/stdc++.h>
#define    ll          long long int
#define    sz          200010
#define    md          1000000007
#define    py          printf("YES\n")
#define    pn          printf("NO\n")
#define    sc1(a)      scanf("%lld",&a)
#define    sc2(a,b)    scanf("%lld %lld",&a,&b)
#define    pv(a)      printf("%lld\n",a)
using namespace std;




int main()
{


    ll a,b,c,d,i,j,p;

    p=1;
    cin>>a>>b>>c>>d;

    while(1)
    {
        if(p%2==1)
        {
            c=c-b;
            p++;
            if(c<=0)
            {
                cout<<"Yes"<<endl;
                return 0;
            }
        }
        else
        {
            a=a-d;
            p++;
            if(a<=0)
            {
                cout<<"No"<<endl;
                return 0;
            }
        }
    }

    return 0;
}
