#include <iostream>
using namespace std;

int calc(int a,int b)
{
    int cnt = 0;
    while(a > 0)
    {
        a-=b;
        ++cnt;
    }
    return cnt;
}

int main()
{
    int a,b,c,d;
    cin >> a >> b >> c >> d;
    int cnt1 = calc(a,d);
    int cnt2 = calc(c,b);
    if(cnt1 >= cnt2)
    {
        cout << "Yes" << endl;
    }
    else
    {
        cout << "No" << endl;
    }
    
}