#include <bits/stdc++.h>
using namespace std;

#define ll long long
#define rep(i, n) for (ll i = 0; i < n; ++i)
#define rep_up(i, a, n) for (ll i = a; i < n; ++i)
#define rep_down(i, a, n) for (ll i = a; i >= n; --i)
#define P pair<ll, ll>

#define all(v) v.begin(), v.end()
#define fi first
#define se second
#define vvvll vector<vector<vector<ll>>>
#define vvll vector<vector<ll>>
#define vll vector<ll>
#define pqll priority_queue<ll>
#define pqllg priority_queue<ll, vector<ll>, greater<ll>>

constexpr ll INF = (1ll << 60);
constexpr ll mod = 1000000007;
constexpr double pi = 3.14159265358979323846;
template <typename T>
inline bool chmax(T &a, T b) {
    if (a < b) {
        a = b;
        return 1;
    }
    return 0;
}
template <typename T>
inline bool chmin(T &a, T b) {
    if (a > b) {
        a = b;
        return 1;
    }
    return 0;
}
ll mypow(ll a, ll n) {
    ll ret = 1;
    rep(i, n) {
        if (ret > (ll)(1e18 + 10) / a) return -1;
        ret *= a;
    }
    return ret;
}
long long modpow(long long a, long long n, long long mod) {
    long long res = 1;
    while (n > 0) {
        if (n & 1) res = res * a % mod;
        a = a * a % mod;
        n >>= 1;
    }
    return res;
}
vector<bool> prime(1000010, true);
vector<bool> isprime(int N) {
    if (N >= 0) prime[0] = false;
    if (N >= 1) prime[1] = false;
    for (ll i = 2; i * i <= N; i++) {
        if (!prime[i]) {
            continue;
        }
        for (ll j = i * i; j <= N; j += i) {
            prime[j] = false;
        }
    }
    return prime;
}
int main(){
    ll a,b,c,d,ans;
    cin>>a>>b>>c>>d;
    if(a==c||b==d||abs(a-c)+abs(b-d)<=3)ans=1;
    else ans=2;
    cout<<ans<<endl;
}