using System;
using System.IO;
using System.Linq;
using System.Text;
using System.Collections.Generic;
using System.Diagnostics;
using System.Numerics;
using Enu = System.Linq.Enumerable;

class Program
{
    static readonly int Mod = (int)1e9 + 7;

    public void Solve()
    {
        int N = Reader.Int();
        BigInteger[] B = new BigInteger[N], M = new BigInteger[N];
        BigInteger[] A = new BigInteger[N];
        for (int i = 0; i < N; i++)
        {
            A[i] = 1;
            B[i] = Reader.Int();
            M[i] = Reader.Int();
        }
        BigInteger x, m;
        LinearCongruence(A, B, M, out x, out m);
        if (m < 0) Console.WriteLine(-1);
        else
        {
            if (x == 0) x += m;
            x %= Mod;
            Console.WriteLine(x);
        }
    }


    // A[i] * X % M[i] = B[i] % M[i]
    // X % m = x
    static void LinearCongruence(BigInteger[] A, BigInteger[] B, BigInteger[] M, out BigInteger x, out BigInteger m)
    {
        x = 0;
        m = 1;
        for (int i = 0; i < A.Length; i++)
        {
            BigInteger a = A[i] * m;
            BigInteger b = B[i] - A[i] * x;
            BigInteger d = BigInteger.GreatestCommonDivisor(M[i], a);
            if (b % d != 0) { x = m = -1; return; }
            BigInteger t = b / d * ModInverse(a / d, M[i] / d) % (M[i] / d);
            x = x + m * t;
            m *= M[i] / d;
        }
        x = (x % m + m) % m;
    }
    static BigInteger ModInverse(BigInteger N, BigInteger mod)
    {
        BigInteger x = 0, y = 0;
        ExtGCD(N, mod, ref x, ref y);
        return (x % mod + mod) % mod;
    }
    static BigInteger ExtGCD(BigInteger a, BigInteger b, ref BigInteger x, ref BigInteger y)
    {
        if (b == 0) { x = 1; y = 0; return a; }
        BigInteger res = ExtGCD(b, a % b, ref y, ref x);
        y -= (a / b) * x;
        return res;
    }

}


class Entry { static void Main() { new Program().Solve(); } }
class Reader
{
    private static TextReader reader = Console.In;
    private static readonly char[] separator = { ' ' };
    private static readonly StringSplitOptions op = StringSplitOptions.RemoveEmptyEntries;
    private static string[] A = new string[0];
    private static int i;
    private static void Init() { A = new string[0]; }
    public static void Set(TextReader r) { reader = r; Init(); }
    public static void Set(string file) { reader = new StreamReader(file); Init(); }
    public static bool HasNext() { return CheckNext(); }
    public static string String() { return Next(); }
    public static int Int() { return int.Parse(Next()); }
    public static long Long() { return long.Parse(Next()); }
    public static double Double() { return double.Parse(Next()); }
    public static int[] IntLine() { return Array.ConvertAll(Split(Line()), int.Parse); }
    public static int[] IntArray(int N) { return Enu.Range(0, N).Select(i => Int()).ToArray(); }
    public static int[][] IntTable(int H) { return Enu.Range(0, H).Select(i => IntLine()).ToArray(); }
    public static string[] StringArray(int N) { return Enu.Range(0, N).Select(i => Line()).ToArray(); }
    public static string Line() { return reader.ReadLine().Trim(); }
    private static string[] Split(string s) { return s.Split(separator, op); }
    private static string Next() { CheckNext(); return A[i++]; }
    private static bool CheckNext()
    {
        if (i < A.Length) return true;
        string line = reader.ReadLine();
        if (line == null) return false;
        if (line == "") return CheckNext();
        A = Split(line);
        i = 0;
        return true;
    }
}