/******************************************************************************

                              Online C++ Compiler.
               Code, Compile, Run and Debug C++ program online.
Write your code in this editor and press "Run" button to compile and execute it.

*******************************************************************************/

#include <iostream>
#include <utility>
#include <vector>
#include <algorithm>
using namespace std;

int main()
{
    int A, B, C, D;
    cin>>A>>B>>C>>D;
    
    while(A>0 && C>0){
        C-=B;
        A -=D;
        if(C<=0){
            cout<<"Yes";
        }
        else if (A<=0){
            cout<<"No";
        }
    }
    
}
