#include<bits/stdc++.h>
using namespace std;
using Int = long long;
//INSERT ABOVE HERE
signed main(){
  Int x,y,a,b;
  cin>>x>>y>>a>>b;
  if(x<0) x*=-1,a*=-1;
  if(y<0) y*=-1,b*=-1;
  Int ans=max(x,y);
  if(x==y&&a==b&&a>0) ans++;
  cout<<ans<<endl;
  return 0;
}