#include <iostream>
#include <vector>
#include <algorithm>
#include <iomanip>
using namespace std;

typedef long long LL;

LL iabs(LL n){
    if(n < 0) return -n;
    return n;
}

int main(){
    int x, y, x2, y2;
    cin >> x >> y >> x2 >> y2;
    LL ans = 0;
    if(y >= 0){
        ans += max(iabs(x), iabs(y));
        if(iabs(x) == iabs(y) && iabs(x2) == iabs(y2) && iabs(x) > iabs(x2) && x/y == x2/y2){
            ans += 1;
        }
        if(y == 0 && ((x < 0 && x < x2 && x2 < 0) || (x > 0 && x2 < x && x2 > 0))){
            ans += 1;
        }
    }else{
        ans += iabs(x) + iabs(y);
        if(x == 0 && y < y2 && y2 < 0){
            ans += 2;
        }
    }
    cout << ans << endl;
    return 0;
}