#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for(int i = 0; i < n; i++)
#define rep2(i, x, n) for(int i = x; i <= n; i++)
#define rep3(i, x, n) for(int i = x; i >= n; i--)
#define elif else if
#define sp(x) fixed << setprecision(x)
#define pb push_back
#define eb emplace_back
#define all(x) x.begin(), x.end()
#define sz(x) (int)x.size()
using ll = long long;
using pii = pair<int, int>;
using pil = pair<int, ll>;
using pli = pair<ll, int>;
using pll = pair<ll, ll>;
const int MOD = 1000000007;
//const int MOD = 998244353;
const int inf = (1<<30)-1;
const ll INF = (1LL<<60)-1;
const double pi = acos(-1.0);
const double EPS = 1e-10;
template<typename T> bool chmax(T &x, const T &y) {return (x < y)? (x = y, true) : false;};
template<typename T> bool chmin(T &x, const T &y) {return (x > y)? (x = y, true) : false;};

template<typename T>
struct Euclid{
    Euclid() = default;

    T gcd(const T &a, const T &b) const{
        if(b == 0) return a;
        else return gcd(b, a%b);
    }

    T lcm(const T &a, const T &b) const {return a*(b/gcd(a,b));}

    T extgcd(const T &a, const T &b, T &x, T &y) const{
        if(b == 0) {x = 1, y = 0; return a;}
        T g = extgcd(b, a%b, y, x);
        y -= (a/b)*x;
        return g;
    }

    T mod(const T &a, const T &m) const{
        T ret = a%m;
        return ret+(ret < 0? m : 0);
    }

    T modinv(const T &a, const T &m) const{ //aとmは互いに素
        T x, y;
        extgcd(a, m, x, y);
        return mod(x, m);
    }

    T floor_sum(const T &n, const T &m, T a, T b) const{ //Σ(floor((a*i+b)/m)) (0<=i<n)
        T ret = (a/m)*(n*(n-1)/2) + (b/m)*n;
        a %= m, b %= m;
        T y = (a*n+b)/m;
        if(y == 0) return ret;
        ret += floor_sum(y, a, m, a*n-(m*y-b));
        return ret;
    }

    pair<T, T> Chinese_rem(const T &a1, const T &m1, const T &a2, const T &m2) const{
        T x, y, g = extgcd(m1, m2, x, y);
        if((a2-a1)%g != 0) return make_pair(0, -1);
        T m = m1*(m2/g);
        T tmp = mod((x*((a2-a1)/g)), m2/g);
        T a = (m1*tmp+a1) % m;
        return make_pair(a, m);
    }

    T Garner(vector<T> a, vector<T> m, const T &M) const{
        m.pb(M);
        vector<T> coeffs(sz(m), 1);
        vector<T> constants(sz(m), 0);
        rep(k, sz(a)){
            T t = mod((a[k]-constants[k]) * modinv(coeffs[k], m[k]), m[k]);
            rep2(i, k+1, sz(m)-1){
                constants[i] += t*coeffs[i], constants[i] %= m[i];
                coeffs[i] *= m[k], coeffs[i] %= m[i];
            }
        }
        return constants.back();
    }
};

int main(){
    int N;
    cin >> N;
    vector<ll> a(N), m(N);
    rep(i, N) cin >> a[i] >> m[i];
    Euclid<ll> E;
    ll l = 1;
    rep(i, N){
        rep(j, i){
            ll g = E.gcd(m[i], m[j]);
            if((a[i]-a[j])%g != 0) {cout << -1 << endl; return 0;}
            m[i] /= g, m[j] /= g;
            ll gi = gcd(m[i], g), gj = g/gi;
            do{
                g = gcd(gi, gj);
                gi *= g, gj /= g;
            } while(g != 1);
            m[i] *= gi, m[j] *= gj;
            a[i] %= m[i], a[j] %= m[j];
        }
    }
    rep(i, N) l *= m[i], l %= MOD;
    bool flag = true;
    rep(i, N) if(a[i] != 0) flag = false;
    if(flag) {cout << l << endl; return 0;}
    cout << E.Garner(a, m, MOD) << endl;
}