#include <bits/stdc++.h>
using namespace std;
#define ll long long
int main() {
  int a,b,c,d;
  cin>>a>>b>>c>>d;
  int e=a/b;
  int f=c/d;
  int g=a%b;
  int h=c%d;
  if(e>f){coout<<"Yes"<<endl;}
  if(e=f){if(h==0){cout<<"No"<<endl;}else{cout<<"Yes"<<endl;}}
  if(e<f){cout<<"No"<<endl;}
}