#include <bits/stdc++.h>
using namespace std;
int main(){
  int a,b,c,d;
  cin >> a >> b >> c >> d;
  while(a=0;a <= 0;a++){
    a-b;
  }
  while(c=0;c <= 0;c++){
  c-d;
  }
  if(a==0)
  cout<<"yes"<<endl;
  if(c==0)
    cout<<"no"<<endl;
}
    
   
  