#include<bits/stdc++.h>
using namespace std;
int main(){
    int a,b,c,d;
    cin >> a >> b >> c >> d;
    bool takahashi = true;
    while(a>0 && c>0){
        if(takahashi){
            c -= b;
            takahashi = false;
        }else{
            a -= d;
            takahashi = true;
        }
    }
    if(!takahashi)cout <<"Yes"<<endl;
    else cout <<"No"<<endl;
    
}
