// Author: HarshKumar

#include <bits/stdc++.h>
using namespace std;
#define ll int64_t
const ll N = 1e6 + 6, M = 1e9 + 7;
int main()
{
    ios::sync_with_stdio(false), cin.tie(nullptr);
    ll a, b, c, d, f = 0;
    cin >> a >> b >> c >> d;
    while (a > 0 && c > 0)
    {
        if (f)
            a -= d;
        else
            c -= b;
        f ^= 1;
    }
    cout << (a > 0 ? "Yes" : "No");
}