// Author: Teoman Ata Korkmaz
#include <bits/stdc++.h>
#define int int_fast64_t
using namespace std;
///////////////////////////////////////////////////////////
int n,mnx,mny;
vector<tuple<int,int>> v;
signed main(void){
cin>>n;
int x,y,a,b;
for(int i=0;i<n;i++){
cin>>x>>y;
if(!i)a=x,b=y;
v.push_back({x-a,y-b});
}
for(auto [a,b]:v){
cerr<<"v:"<<a<<","<<b<<endl;
}
int ansx=0,ansy=0;
for(int i=0;i<n;i++){
for(int j=i+1;j<n;j++){
// cerr<<"i,j:"<<i<<" "<<j<<endl;
auto [xi,yi]=v[i];
auto [xj,yj]=v[j];
if(xi<0)xi*=-1,yi*=-1;
if(yi<0)xj*=-1,yj*=-1;
int a=(xi==xj) ? yi : yi*(xj/gcd(xi,xj));
int b=(xi==xj) ? yj : yj*(xi/gcd(xi,xj));
// cerr<<"a";
ansx=gcd(ansx,abs(a-b));
// cerr<<"a";
if(xj<0)xi*=-1,yi*=-1;
if(yj<0)xj*=-1,yj*=-1;
// cerr<<"a";
a=(yi==yj) ? xi : xi*(yj/gcd(yi,yj));
b=(yi==yj) ? xi : xj*(yi/gcd(yi,yj));
// cerr<<"a";
ansy=gcd(ansy,abs(a-b));
// cerr<<"a"<<endl;
}
}
cout<<(ansx && ansy ? (ansx/gcd(ansx,ansy))*ansy : -1)<<endl;
}
