#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

typedef long long ll;

const int INF = int(3e9);

int main(void){
    ll a , b , c , d;
    cin >> a >> b >> c >> d;
    if (a == c && b == d) {
        cout << 0 << endl;
        exit(0);
    }

    vector<pair<ll , ll>> moving;
    for (int i = -3; i <= 3; i++) {
        for (int j = -3; j <= 3; j++) {
            if (i == 0) continue;
            if (j == 0) continue;
            int cost = abs(i) + abs(j);
            if(cost > 3)continue;
            moving.emplace_back(a + i , b + j);
        }
    }
    
    int ans1 = INF;
    for (int i = 0; i < moving.size(); i++) {
        if (moving[i].first == c && moving[i].second == d) {
            ans1 = 1;
            break;
        }
    }
    int ans2 = abs(a - c) + 1;
    int ans3 = abs(b - d) + 1;
    //cout << ans1 << " : " << ans2 << " : " << ans3 << endl;
    cout << min({ans1 , ans2 , ans3}) << endl;
    return 0;
}