#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N = 3e5 + 12, MOD = (int)1e9 + 7;
int n, x[N], y[N];
ll G = 0;
vector<array<ll, 2>> a;
array<ll, 2> Gcd(array<ll, 2> c,array<ll, 2> d) {
if(!c[0]) {
G = gcd(G, c[1]);
return d;
}
if(!d[0]) {
G = gcd(G, d[1]);
return c;
}
if(c[0] < d[0]) {
swap(c, d);
}
ll col = c[0] / d[0];
c[0] -= col * 1ll * d[0];
c[1] -= col * 1ll * d[1];
return Gcd(c, d);
}
void test() {
cin >> n;
for(int i = 1; i <= n; i++) {
cin >> x[i] >> y[i];
}
for(int i = 2; i <= n; i++) {
if(x[i] == x[i - 1]) {
G = gcd(G, y[i] - y[i - 1]);
continue;
}
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]});
}
}
// for(auto [x, y]:a) {
// cout << x << ' ' << y << '\n';
// }
while((int)a.size() >= 2) {
auto i = a.back();
a.pop_back();
auto k = Gcd(i, a[0]);
a[0] = k;
}
if(a.empty() || !a[0][0]) {
cout << -1 << '\n';
return;
}
cout << G * 1ll * (a[0][0]) << '\n';
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(0);
int t = 1;
// cin >> t;
while(t--)
test();
return 0;
}
