#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const long long INF = 1LL << 60;
const int mod = 1e9 + 7;

int main()
{
    int a, b, c, d;
    cin >> a >> b >> c >> d;
    string ans;
    int tk, ao;

    if (a % d != 0)
    {
        tk = a / d + 1;
    }
    else
    {
        tk = a / d;
    }

    if (c % b != 0)
    {
        ao = c / b + 1;
    }
    else
    {
        ao = c / b;
    }
    if (tk >= ao)
    {
        ans = "Yes";
    }
    else
    {
        ans = "No";
    }
    cout << ans << endl;
    return 0;
}