#include <bits/stdc++.h>
using namespace std;
int main(){
int x,y,a,b;cin>>x>>y>>a>>b;
if (x == y) {
 cout << (a == b ? x + 1 : x) << endl;
} else if (x == 0) {
  cout << (a == 0 ? y + 1 : y) << endl;
} else if (y == 0) {
cout << (b == 0 ? x + 1 : x) << endl;
} else {
cout << max(a, b) << endl;
}
}