#include <bits/stdc++.h>
using namespace std;
int main() {
int x,y,z,w;
  cin>>x>>y>>z>>w;
   while(x>0&&y>0){
  z-=y;
  if (z<=0){
    cout<<"Yes"<<endl;}
     x-=w;
    if(x<=0){
      cout<<"No"<<endl;}
    else {
      continue;
    }
  }
}