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

#define int long long

struct DSU {
	vector<int> v;
	vector<vector<int>> c;

	DSU(int n) : v(n), c(n) {
		for (int i = 0; i < n; i++) {
			v[i] = i;
			c[i].push_back(i);
		}
	}

	int find(int a) {
		return v[a] == a ? a : v[a] = find(v[a]);
	}

	bool unite(int a, int b) {
		a = find(a);
		b = find(b);
		if (a == b) {
			return true;
		}
		if (c[a].size() < c[b].size()) {
			swap(a, b);
		}
		c[a].insert(c[a].end(), c[b].begin(), c[b].end());
		c[b].clear();
		v[b] = a;
		return false;
	}
};

int sign(int x) {
	return (x > 0) - (x < 0);
}

int cross(int x1, int y1, int x2, int y2) {
	return x1 * y2 - y1 * x2;
}

int orient(int x1, int y1, int x2, int y2, int x3, int y3) {
	return sign(cross(x1 - x2, y1 - y2, x3 - x2, y3 - y2));
}

bool test(int x1, int y1, int x2, int y2, int x3, int y3, int x4, int y4) {
	int o1 = orient(x1, y1, x2, y2, x3, y3);
	int o2 = orient(x1, y1, x2, y2, x4, y4);
	int o3 = orient(x3, y3, x4, y4, x1, y1);
	int o4 = orient(x3, y3, x4, y4, x2, y2);
	return o1 != o2 && o3 != o4;
}

signed main(){
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int N;
	cin>>N;
	struct Pt{ 
		int x,y; 
	};
	vector<Pt>v(N);
	for(int i=0;i<N;i++){
		cin>>v[i].x>>v[i].y;
	}
	vector<pair<int,pair<int,int>>>e;
	for(int i=0;i<N;i++){
		for(int j=i+1;j<N;j++){
			e.emplace_back((v[i].x-v[j].x)*(v[i].x-v[j].x)+(v[i].y-v[j].y)*(v[i].y-v[j].y),make_pair(i,j));
		}
	}
	sort(e.begin(),e.end());
	DSU dsu(N);
	vector<vector<int>>dp(N,vector<int>(N,0));
	auto T=[&](int i,int j)->bool{
		return test(v[i].x,v[i].y,v[j].x,v[j].y,0,0,1e9+7,1e9+9);
	};
	for(int i=0;i<e.size();){
		int ans=e[i].first;
		while(i<e.size()&&e[i].first==ans){
			auto[a,b]=e[i].second;
			int ca=dsu.find(a),cb=dsu.find(b);
			if(ca==cb){
				if(dp[a][b]^T(a,b)){
					cout<<ans<<'\n';
					return 0;
				}
			}
			else {
				int x=T(a,b);
				for(int i:dsu.c[ca]){
					for(int j:dsu.c[cb]){
						dp[i][j]=dp[j][i]=dp[i][a]^x^dp[j][b];
					}
				}
				dsu.unite(a,b);
			}
			i++;
		}
	}
	cout<<-1<<'\n';
	return 0;
}