#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
typedef pair<ll,ll> P;
typedef vector<ll> VI;
typedef vector<VI> VVI;
#define REP(i,n) for(ll i=0;i<(n);i++)
#define ALL(v) v.begin(),v.end()
constexpr ll MOD=1000000007;
constexpr ll INF=2e18;

int main(){
    ll a, b, c, d;
    cin >> a >> b >> c >> d;
    c-=a, d-=b;
    if(abs(c)+abs(d)<=3)
        cout << 1 << endl;
    else if(c==0||d==0)
        cout << 1 << endl;
    else
        cout << 2 << endl;
}