#include <vector>
#include <iostream>
#include <algorithm>
#include <cmath>

using namespace std;

int main(){
    int a, b, c,d;
    cin >> a >> b >> c >> d;

    int turn = 0;
    while(a * c >0){
        if(turn==0){
            c -= b;
            turn = 1;
        }
        else{
            a -= d;
            turn = 0;
        }
    }

    cout << (turn == 1 ? "Yes" : "No") << endl;

    return 0;
}