#include <bits/stdc++.h>
using namespace std;

int main(){
    int Ta, Th, Aa, Ah;
    cin >> Th >> Ta >> Ah >> Aa;
    bool f = 1;
    while(Th > 0 && Ah > 0){
        if(f){
            Ah -= Ta;
            f = !f;
        }
        else{
            Th -= Aa;
            f = !f;
        }
    }
    if(Th > 0) cout << "Yes" << endl;
    else cout << "No" << endl;
    return 0;
}
