#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<cctype>
#include<cstdlib>
#include<algorithm>
#include<bitset>
#include<vector>
#include<list>
#include<deque>
#include<queue>
#include<map>
#include<set>
#include<stack>
#include<cmath>
#include<sstream>
#include<fstream>
#include<iomanip>
#include<ctime>
#include<complex>
#include<functional>
#include<climits>
#include<cassert>
#include<iterator>
using namespace std;

int main(){
	long long int x, y, x2, y2;
	scanf("%lld%lld%lld%lld", &x, &y, &x2, &y2);
	long long int xx = abs(y);
	long long int yy = abs(x);
	long long int k = min(xx, yy);
	long long int aa = xx - k + yy - k + k;
	if (xx == yy){
		if (abs(x2) == abs(y2)){
			if (x / abs(x) == x2 / abs(x2) && y / abs(y) == y2 / abs(y2)){
				if (abs(x2) <= abs(x) && abs(y2) <= abs(y)){
					aa ++;
				}
			}
		}
	}
	long long int ans = aa;
	printf("%lld\n", ans);
	return 0;
}