#include <bits/stdc++.h>
using namespace std;

using ll = long long;
#define rep(i, n) for(int i = 0; i < n; i++)

int main() {
	int x, y, x2, y2;
	cin >> x >> y >> x2 >> y2;
	int ans = max(x, y);
	complex<double> c(x, y), c1(x2, y2);
	if(arg(c) == arg(c1)) ans += 2;
	cout << ans << endl;
}