#include <iostream>

using namespace std;

void solve() {
    int sx, sy, gx, gy;
    cin >> sx >> sy >> gx >> gy;

    auto dx = abs(gx - sx),
         dy = abs(gy - sy);

    if (dx == 0 && dy == 0) {
        cout << "0\n";
    } else if (dx == 0 || dy == 0 ||
               (dx <= 3 && dy <= 3 && dx + dy <= 3)) {
        cout << "1\n";
    } else {
        cout << "2\n";
    }
}

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    solve();

    return 0;
}