#include <bits/stdc++.h>
using namespace std;
int main(){
    int A,B,C,D;cin>>A>>B>>C>>D;
    int i=0;
    while(A>0&&C>0){
        if(i%2==0){
            C=C-B;
        }
        if(i%2==1){
            A=A-D;
        }
        i++;
    }
    if(A<=0)cout<<"No"<<endl;
    else cout<<"Yes"<<endl;
}