Problem:
Score : 200 points

Problem Statement

You are given positive integers A and B.

Find the K-th largest positive integer that divides both A and B.

The input guarantees that there exists such a number.

Constraints

All values in input are integers.

1 \leq A, B \leq 100

The K-th largest positive integer that divides both A and B exists.

K \geq 1

Input

Input is given from Standard Input in the following format:

A B K

Output

Print the K-th largest positive integer that divides both A and B.

Sample Input 1

8 12 2

Sample Output 1

2

Three positive integers divides both 8 and 12: 1, 2 and 4.
Among them, the second largest is 2.

Sample Input 2

100 50 4

Sample Output 2

5

Sample Input 3

1 1 1

Sample Output 3

1

Solution in C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.IO;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
using System.Numerics;
using System.Diagnostics;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;
using static System.Math;
using MethodImplOptions = System.Runtime.CompilerServices.MethodImplOptions;
using MethodImplAttribute = System.Runtime.CompilerServices.MethodImplAttribute;
using static Reader;

public static class P
{
    public static void Main()
    {
        var a = NextInt;
        var b = NextInt;
        var k = NextInt;
        Console.WriteLine(Enumerable.Range(1, 100).Where(x => a % x == 0 && b % x == 0).Reverse().Skip(k - 1).First());
    }
}


static class Reader
{
    const int BUF_SIZE = 1 << 12;
    static Stream Stream = Console.OpenStandardInput();
    static byte[] Buffer = new byte[BUF_SIZE];
    static int ptr = BUF_SIZE - 1;
    static void Move() { if (++ptr >= Buffer.Length) { Stream.Read(Buffer, 0, BUF_SIZE); ptr = 0; } }

    public static int NextInt
    {
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        get
        {
            int res = 0; while (Buffer[ptr] < 48) Move();
            do { res = res * 10 + (int)(Buffer[ptr] ^ 48); Move(); } while (48 <= Buffer[ptr]);
            return res;
        }
    }
}