#include<bits/stdc++.h>
using namespace std;
long long d,x,y;
long long gcd(long long a, long long b) {
a = abs(a);
b = abs(b);
if(b == 0) {
return a;
}
return gcd(b,a%b);
}
pair<long long,long long> euclid(long long a, long long b) {
if(b == 0) {
return {1,0};
}
pair<long long,long long> ans;
if(abs(a) < abs(b)) {
ans = euclid(b,a);
return {ans.second,ans.first};
}
else {
long long c = abs(a)/abs(b);
if(a*b < 0) {
c = -c;
}
ans = euclid(a-c*b,b);
return {ans.first,ans.second-c*ans.first};
}
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
long long n;
cin >> n;
if(n <= 2) {
cout << -1;
return 0;
}
long long x0,y0,a,b;
cin >> x0 >> y0;
vector<pair<long long,long long>> haha(0);
for(long long i = 1; i < n; i++) {
cin >> a >> b;
a-=x0;
b-=y0;
haha.push_back({a,b});
}
pair<long long,long long> p1 = haha[0],p2 = {0,0};
for(long long i = 1; i < n-1; i++) {
if(p1.first*haha[i].second != p1.second*haha[i].first) {
p2 = haha[i];
}
}
if(p2.first == 0 && p2.second == 0) {
cout << -1;
return 0;
}
long long e = gcd(p1.second,p2.second);
d = (p1.first*p2.second-p2.first*p1.second)/e;
d = abs(d);
y = e;
pair<long long,long long> q = euclid(p1.second,p2.second);
x = q.first*p1.first+q.second*p2.first;
x = x%d;
for(long long i = 1; i < n-1; i++) {
pair<long long,long long> p = haha[i];
long long e = gcd(p.second,y);
if(p.second == 0) {
d = gcd(d,p.first);
}
else {
d = gcd(d,(x*p.second-y*p.first)/e);
}
y = e;
pair<long long,long long> q = euclid(y,p.second);
x = x*q.first+p.first*q.second;
x%=d;
}
cout << abs(d*y);
return 0;
}
