#include <bits/stdc++.h>
#include<iostream>
#include<iomanip>
#include<string>
#include<algorithm>
#include<vector>
#include<set>
#include<list>
#include<queue>
#include<math.h>
#include<bitset>
using ll = long long;
using namespace std;

int main(){
    int x, y, x2, y2;
    cin >> x >> y >> x2 >> y2;
    if (abs(x)==abs(y) && abs(x2)==abs(y2) && abs(x)*y2 == abs(x2)*y && x*abs(y2)==x2*abs(y) && abs(x) > abs(x2)){
        cout << max(abs(x), abs(y)) + 1 << endl;
    } else cout << max(abs(x), abs(y)) << endl;   
}