#include <iostream>
using namespace std;


int main() {
    int a,b,c,d;
    cin >> a >> b >> c >> d;
    
    int sw = 0;
    while (a > 0 || c > 0) {
        if (sw == 0) {
            c -= b;
            sw = 1;
        } else {
            a -= d;
            sw = 0;
        }
    }
    
    if (sw == 1) {
        cout << "No" << endl;
    } else {
        cout << "Yes" << endl;
    }
}