#include <bits/stdc++.h>
using namespace std;
int main()
{
    int A, B, C, D;
    cin >> A >> B >> C >> D;
    for (int i = 0;;i++) {
        if (i%2 == 0) {
            C-=B;
        }
        else {
            A -= D;
        }

        if (A <= 0) {
            cout << "No" << endl;break;
        } 
        if (C<= 0) {
            cout << "Yes" << endl;break;
        }
    }
}