#include <bits/stdc++.h>

using namespace std;

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    int a, b, c, d;
    cin >> a >> b >> c >> d;
    int T = a / d + (a%d > 0);
    int A = c/ b + (c%b > 0);
    if (T >= A)
    {
        cout << "Yes";
    }
    else
    {
        cout << "No";
    }
    
}