#include <bits/stdc++.h>
using namespace std;
#define int long long
int ans_x = 0;
int gcd(int a, int b) {
if (a < 0) a *= -1;
if (b < 0) b *= -1;
if (b > a) swap(a, b);
if (b == 0) return a;
return gcd(b, a%b);
}
pair<int, int> zero_vector (pair<int, int> a, pair<int, int> b) {
if (a.first < 0) a = {-a.first, -a.second};
if (b.first < 0) b = {-b.first, -b.second};
if (b.first > a.first) swap(a, b);
if (b.first == 0) {ans_x = gcd(ans_x, b.second); return a;}
return zero_vector(b, {a.first%b.first, a.second-b.second*(a.first/b.first)});
}
signed main() {
int n; cin >> n;
if (n < 3) {cout << -1; return 0;}
int x[n], y[n];
for (int i = 0; i < n; i++) {cin >> x[i] >> y[i];}
vector <pair<int, int>> a;
for (int i = 1; i < n; i++) {
if (x[i] == x[i-1]) {
ans_x = gcd(ans_x, y[i]-y[i-1]);
}
else if (x[i] > x[i-1]) {
a.push_back({x[i]-x[i-1], y[i]-y[i-1]});
}
else a.push_back({x[i-1]-x[i], y[i-1]-y[i]});
}
while (a.size() >= 2) {
auto i = a.back();
a.pop_back();
a[0] = zero_vector(a[0], i);
}
if (a.size() == 0 or a[0].first == 0 or ans_x == 0) cout << -1;
else cout << a[0].first*ans_x;
}
