#include<bits/stdc++.h>
#include <boost/multiprecision/cpp_int.hpp>
using namespace std;
namespace mp = boost::multiprecision;
using ll = long long;
using Bint = mp::cpp_int;

Bint safe_mod(Bint x, Bint m) {
    x %= m;
    if (x < 0) x += m;
    return x;
}

std::pair<Bint, Bint> inv_gcd(Bint a, Bint b) {
    a = safe_mod(a, b);
    if (a == 0) return {b, 0};
    Bint s = b, t = a;
    Bint m0 = 0, m1 = 1;

    while (t) {
        Bint u = s / t;
        s -= t * u;
        m0 -= m1 * u;
        auto tmp = s;
        s = t;
        t = tmp;
        tmp = m0;
        m0 = m1;
        m1 = tmp;
    }
    if (m0 < 0) m0 += b / s;
    return {s, m0};
}

std::pair<Bint, Bint> crt(const std::vector<Bint>& r,
                                    const std::vector<Bint>& m) {
    assert(r.size() == m.size());
    int n = int(r.size());
    Bint r0 = 0, m0 = 1;
    for (int i = 0; i < n; i++) {
        assert(1 <= m[i]);
        Bint r1 = safe_mod(r[i], m[i]), m1 = m[i];
        if (m0 < m1) {
            std::swap(r0, r1);
            std::swap(m0, m1);
        }
        if (m0 % m1 == 0) {
            if (r0 % m1 != r1) return {0, 0};
            continue;
        }
        Bint g, im;
        std::tie(g, im) = inv_gcd(m0, m1);
        Bint u1 = (m1 / g);
        if ((r1 - r0) % g) return {0, 0};
        Bint x = (r1 - r0) / g % u1 * im % u1;
        r0 += x * m0;
        m0 *= u1;
        if (r0 < 0) r0 += m0;
    }
    return {r0, m0};
}

int main(){
    int n;
    cin >> n;
    vector<Bint> r(n), m(n);
    for(int i = 0; i < n; i++){
        cin >> r[i] >> m[i];
    }
    auto ans = crt(r, m);
    if(ans.second == 0){
        cout << -1 << '\n';
        return 0;
    }
    cout << ans.first % 1000000007 << '\n';
}