using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    static int[][] NArr(long n) => Enumerable.Repeat(0, (int)n).Select(_ => NList).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var t = NN;
        var ans = new long[t];
        for (var u = 0; u < t; ++u)
        {
            var c = NList;
            ans[u] = Div(c[0], c[1]);
        }
        WriteLine(string.Join("\n", ans));
    }
    static long Div(int a, int b)
    {
        var sq = (int)Math.Sqrt(b) + 10;
        var ans = long.MaxValue;
        for (var i = 0L; i <= sq; ++i)
        {
            if ((b + i) % (a + i) == 0)
            {
                ans = i;
                break;
            }
        }
        for (long i = sq; i > 1; --i)
        {
            if (b > i * a && (b - i * a) % (i - 1) == 0)
            {
                ans = Math.Min(ans, (b - i * a) / (i - 1));
                break;
            }
        }
        if (ans == long.MaxValue) ans = -1;
        return ans;
    }
}