#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);
    }

    for (int i = -2; i <= 2; i++) {
        for (int j = -2; j <= 2; j++) {
            int cost = abs(i) + abs(j);
            if(cost > 3)continue;
            if (a + i == c && b + j == d) {
                cout << 1 << endl;
                exit(0);
            }
        }
    }
    
    ll ans1 = abs(a - c) + 1;
    ll ans2 = abs(b - d) + 1;
    cout << (min(abs(a - c) , abs(b - d)) + (ll)1) << endl;
    return 0;
}