#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
int main(){
    ll x,y,x2,y2;cin>>x>>y>>x2>>y2;
    ll res = max(x,y);
    if(abs(x) == abs(y) && abs(x2) == abs(y2) && abs(x) > abs(x2)){
        res++;
    }
    cout << res << endl;
}