#include <bits/stdc++.h>
using namespace std;
#define int long long
int cross(array<int,2>a, array<int,2>b){
return (a[0]*b[1]-b[0]*a[1]);
}
pair<int,int> euclid(int a, int b){
if(b==0){
return {1,0};
}
pair<int,int>ans = euclid(b,a%b);
swap(ans.first,ans.second);
ans.second-=(a/b)*ans.first;
return ans;
}
signed main(){
ios::sync_with_stdio(0);
cin.tie(0);
int n;
cin >> n;
array<int,2>pts[n];
for(int i = 0;i<n;i++){
cin >> pts[i][0];
cin >> pts[i][1];
}
if(n<=2){
cout << -1;
return 0;
}
for(int i = n-1;i>=0;i--){
pts[i][0]-=pts[0][0];
pts[i][1]-=pts[0][1];
}
array<int,2>pt1 = pts[1];
array<int,2>pt2 = {0,0};
for(int i = 2;i<n;i++){
if(cross(pt1,pts[i])){
pt2=pts[i];
break;
}
}
if(pt2==(array<int,2>){0,0}){
cout << -1;
return 0;
}
int y = gcd(pt1[1],pt2[1]);
int d = abs(cross(pt1,pt2))/y;
pair<int,int>p = euclid(pt1[1],pt2[1]);
int x = p.first*pt1[0]+p.second*pt2[0];
x%=d;
for(int i = 1;i<n;i++){
if(pts[i][1]==0){
///only x coord
d=gcd(d,pts[i][0]);
}
else{
///potentially both
d=gcd(d,(pts[i][1]*x-y*pts[i][0])/gcd(y,pts[i][1]));
d=abs(d);
p=euclid(y,pts[i][1]);
x=x*p.first+pts[i][1]*p.second;
y=gcd(y,pts[i][1]);
}
x%=d;
}
cout << abs(d*y);
return 0;
}
