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

#define int long long

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());
	vector<vector<int>>g(N);
	vector<int>p;
	auto dfs=[&](auto self,int i,int j,int t)->bool{
		if(j==t){
			p.push_back(j);
			return true;
		}
		for(int k:g[j]){
			if(k==i){
				continue;
			}
			if(self(self,j,k,t)){
				p.push_back(j);
				return true;
			}
		}
		return false;
	};
	auto check=[&]()->bool{
		int c=0;
		for(int i=0;i<p.size();i++){
			int j=(i+1)%p.size();
			c+=test(v[p[i]].x,v[p[i]].y,v[p[j]].x,v[p[j]].y,0,0,1e9+7,1e9+9);
		}
		return c%2;
	};
	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;
			p.clear();
			if(dfs(dfs,-1,a,b)){
				if(check()){
					cout<<ans<<'\n';
					return 0;
				}
			}
			else {
				g[a].push_back(b);
				g[b].push_back(a);
			}
			i++;
		}
	}
	cout<<-1<<'\n';
	return 0;
}