#include<iostream>
using namespace std;
int main()
{
    int A,B,C,D,i=0;
    cin>>A>>B>>C>>D;
    while(A>0&&C>0)
    {
        if(i%2==0)
        {
            C=C-B;
            i++;
        }
        else
        {
            A=A-C;
            i++;
        }
    }
    if(A<=0)
        cout<<"No";
    else
        cout<<"Yes";
    return 0;
}
