#include<bits/stdc++.h>
using namespace std;
using ll = long long int;
using ld = long double;
#define pow(n,m) powl(n,m);
#define sqrt(n) sqrtl(n);
const ll MAX = 5000000000000000000;
const ll MOD = 1000000007;
//998244353;
void randinit(){srand((unsigned)time(NULL));}
int main(){
    ll A,B,C,D,X,Y;
    cin >> A >> B >> C >> D;
    X = abs(C - A);
    Y = abs(D - B);
    if(X == 0 || Y == 0 || X + Y <= 3) cout << 1 << endl;
    else cout << 2 << endl;
}