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

// #define int long long
using ll= long long;
#define fo(i,b) for(int i = (0); i < (b); ++i)
#define f(i,a,b) for(int i = (a); i < (b); ++i)
#define rep(i,a,b) for(int i = (a); i < (b); ++i)
typedef pair<int, int> pii;
typedef vector<int> vi;

#define D if(0)

const int NMAX = 112345;
const ll LC   = 2123456789;
const ll NONE = 1003456789;

struct P{
	vector<ll> near;
	int comp;
};
unordered_map<ll, P> p;
unordered_map<ll, int> comp_con;

ll dirs[4] = {-1, 1, -LC, LC};


void resp(int v){
	printf("%d\n", v);
	exit(0);
}
void go_comp(ll x, ll from, int comp)
{
	if(p.count(x)){
		if(p[x].comp) resp(0);
		else
		{
			p[x].comp = comp;
			for(ll near: p[x].near)
			{
				if(near != from) go_comp(near, x, comp);
			}
		}
	}
}
signed main() {
	int n;
	scanf("%d", &n);
	fo(i,n)
	{
		int a,b,c,d;
		scanf("%d%d%d%d", &a, &b, &c, &d);
		ll x = a*LC + b;
		ll y = c*LC + d;
		p[x].near.push_back(y);
		p[y].near.push_back(x);
	}

	int comp_aloc=1;
	for(auto it: p){
		ll x= it.first;
		P str = it.second;
		if(!str.comp) go_comp(x, NONE, ++comp_aloc);
	}


	for(auto it: p){
		ll x= it.first;
		P str = it.second;
		for(ll d : dirs)
		{
			for(ll near: p[x].near) if(x+d == near) goto next;
			if(p.count(x+d))
			{
				if(p[x+d].comp == str.comp) resp(1);
				ll cp = str.comp*LC + p[x+d].comp;
				comp_con[cp]++; 
			}
			next:;
		}
	}
	for(auto it: comp_con) if(it.second > 1) resp(2);
	for(auto it: p){
		ll x= it.first;
		P str = it.second;
		if(str.near.size() >=2)
		{
			if(str.near.size() >=3)
				resp(2);
			ll a = str.near[0];
			ll b = str.near[1];
			if(a+b != x+x) resp(2);

		}
	}
	if(n) resp(3);
	resp(4);

}