#include <iostream>
#include <cstdlib>
#include <algorithm>

using namespace std;

int main() {
	int x, y, x2, y2;
	cin >> x >> y >> x2 >> y2;
	int result = min(x, y) + abs(x - y);
	if (x == y && x2 == y2 && abs(x2) < abs(x)) {
		result += 2;
	}
	cout << result << endl;
	return 0;
}