#include <bits/stdc++.h>

#pragma GCC optimize("O3")
//#define int long long

using namespace std;

int fnd(int x, vector<int> &p){
	if(p[x] < 0) return x;
	return p[x] = fnd(p[x],p);
}

void mrg(int x, int y, vector<int> &p, int out){
	x = fnd(x,p), y = fnd(y,p);
	if(x == y){
		cout << out << "\n";
		exit(0);
	}
	if(p[x] > p[y]) swap(x,y);
	p[x] += p[y];
	p[y] = x;
}

signed main(){
	cin.tie(0);
	ios::sync_with_stdio(0);
	int m;
	cin >> m;
	map<pair<int,int>,int> pti; // point to index
	set<tuple<int,int,int,int>> edges;
	int sol = 3;
	vector<pair<int,int>> points;
	vector<int> ch, cv; // connected horizontally, vertically
	vector<pair<int,int>> e;
	for(int i = 0; i < m; i++){
		int x, y, X, Y;
		cin >> x >> y >> X >> Y;
		if(!pti.count({x,y})){
			pti[{x,y}] = points.size(), points.push_back({x,y});
			cv.push_back(0), ch.push_back(0);
		}
		if(!pti.count({X,Y})){
			pti[{X,Y}] = points.size(), points.push_back({X,Y});
			cv.push_back(0), ch.push_back(0);
		}
		edges.insert({x,y,X,Y});
		edges.insert({X,Y,x,y});
		e.push_back({pti[{x,y}],pti[{X,Y}]});
		if(x != X){
			ch[pti[{x,y}]] = 1;
			ch[pti[{X,Y}]] = 1;
			if(edges.count({x,y-1,X,Y-1}) || edges.count({x,y+1,X,Y+1})){
				sol = 2;
			}
		}
		else{
			cv[pti[{x,y}]] = 1;
			cv[pti[{X,Y}]] = 1;
			if(edges.count({x-1,y,X-1,Y}) || edges.count({x+1,y,X+1,Y})){
				sol = 2;
			}
		}
	}
	int n = points.size();
	for(int i = 0; i < n; i++){
		if(cv[i] && ch[i]) sol = 2;
	}
	vector<int> p(n,-1);
	for(auto t : e){
		int a,b;
		tie(a,b) = t;
		mrg(a,b,p,0);
	}
	for(int i = 0; i < n; i++){
		int x,y;
		tie(x,y) = points[i];
		pair<int,int> dir[] = {{0,1},{1,0},{0,-1},{-1,0}};
		for(int k = 0; k < 4; k++){
			int X = x+dir[k].first, Y = y+dir[k].second;
			if(!pti.count({X,Y})) continue;
			if(edges.count({x,y,X,Y})) continue;
			if(fnd(i, p) == fnd(pti[{X,Y}],p)){
				cout << "1\n";
				exit(0);
			}
		}
	}
	cout << sol << "\n";
}