#include <bits/stdc++.h>
 
using namespace std;
 
int main()
{
    int a, b, c, d;
    cin >> a >> b >> c >> d;

    int aoki = c;
    int taka = a;

    for (int i = 1; i < 100; i++)
    {
        while (aoki > b+1 || taka > d+1)
        {
            aoki = aoki - b;
            taka = taka - d;
        }
        
    }

    aoki = aoki - b;

    if (aoki <= 0)
    {
        cout << "Yes" << endl;
    }
    else
    {
        cout << "No" << endl;
    }
    
    
}
