#include <bits/stdc++.h>

using namespace std;

inline long long mod(long long a, long long m) {
    long long res = a % m;
    if (res < 0) res += m;
    return res;
}

long long extGCD(long long a, long long b, long long& p, long long& q) {
    if (b == 0) { p = 1; q = 0; return a; }
    long long d = extGCD(b, a % b, q, p);
    q -= a / b * p;
    return d;
}


long long modinv(long long a, long long m) {
    long long x, y;
    extGCD(a, m, x, y);
    return mod(x, m); 
}

long long int gcd(long long int x, long long int y)
{
    if (y == 0)
    {
        return x;
    }
    return gcd(y, x % y);
}

pair<long long int,long long int> Garner(vector<long long> b, vector<long long> m, long long MOD) {
    for (int i = 0; i < b.size(); i++)
    {
        for (int j = 0; j < i; j++)
        {
            long long g = gcd(m[i], m[j]);
            if ((b[i] - b[j]) % g != 0)
            {
                return { 0,0 };
            }
            m[i] /= g;
            m[j] /= g;
            long long int gi = gcd(m[i], g);
            long long int gl = g / gi;
            do
            {
                g = gcd(gi, gl);
                gi *= g;
                gl /= g;
            } while (g != 1);
            m[i] *= gi;
            m[j] *= gl;
            b[i] %= m[i];
            b[j] %= m[j];
        }
    }
    m.push_back(MOD); // banpei
    vector<long long> coeffs((int)m.size(), 1);
    vector<long long> constants((int)m.size(), 0);
    for (int k = 0; k < (int)b.size(); ++k) {
        long long t = mod((b[k] - constants[k]) * modinv(coeffs[k], m[k]), m[k]);
        for (int i = k + 1; i < (int)m.size(); ++i) {
            (constants[i] += t * coeffs[i]) %= m[i];
            (coeffs[i] *= m[k]) %= m[i];
        }
    }
    return { constants.back(),coeffs.back() };
}
int main(void)
{
	cin.tie(0);
	ios::sync_with_stdio(false);

    int n;

    cin >> n;
    vector <long long int> x(n), y(n);

    for (int i = 0; i < n; i++)
    {
        cin >> x[i] >> y[i];
    }

    auto it = Garner(x, y, 1e9 + 7);
   // cout << it.first << ' ' << it.second << '\n';
    if (it.second == 0)
    {
        cout << -1 << '\n';
        return 0;
    }
    cout << it.first << '\n';
    return 0;
}