#include <bits/stdc++.h>
using namespace std;
 
int main() {
    double  A,B,C,D;
    cin >> A >> B >> C >> D;
 
    if (ceil(A/D) >= ceil(C/B)) {
        cout << "Yes" << endl;
    } else {
        cout << "No" << endl;
    }

 
    return 0;
}
 