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

int main(){
	long long x,y;
	cin >> x >> y;
	long long x2,y2;
	cin >> x2 >> y2;
	long long count = 0;
	long long a = 0, b = 0;
	while(1){
		if(a == x and b == y) break;
		if(x > a) a++;
		else if(x < a) a--;
		if(y > b) b++;
		else if(y < b) b--;
		if(a == x2 and b == y2) b--;
		count++;
	}
	cout << count << endl;
	return 0;
}