Problem:
Twin Prime

Prime numbers are widely applied for cryptographic and communication technology.
A twin prime is a prime number that differs from another prime number by 2.
For example, (5, 7) and (11, 13) are twin prime pairs.

In this problem, we call the greater number of a twin prime "size of the twin prime."

Your task is to create a program which reads an integer n and prints a twin prime which has the maximum size among twin primes less than or equals to n

You may assume that 5 ≤ n ≤ 10000.

Input

The input is a sequence of datasets. The end of the input is indicated by a line containing one zero. Each dataset is formatted as follows:

n (integer)

Output

For each dataset, print the twin prime p and q (p < q). p and q should be separated by a single space.

Sample Input

12
100
200
300
0

Output for the Sample Input

5 7
71 73
197 199
281 283

Solution in C# (judge verdict: Accepted)

using System;
using System.Collections.Generic;

namespace _0150
{
    class Program
    {
        static void Main(string[] args)
        {
            List<int> sosuu = new List<int>();
            for (int i = 2; i < 10000; i++)
            {
                bool b = true;
                for (int j = 0; j < sosuu.Count; j++)
                {
                    if (i % sosuu[j] == 0)
                    {
                        b = false;
                    }
                }
                if (b)
                {
                    sosuu.Add(i);
                }
            }
            while (true)
            {
                int n = int.Parse(Console.ReadLine());
                if (n == 0)
                {
                    break;
                }
                bool find = true;
                int x = 0;
                for (int i = n; find; i--)
                {
                    if (sosuu.Contains(i) && sosuu.Contains(i - 2))
                    {
                        x = i;
                        find = false;
                    }
                }
                Console.WriteLine((x - 2) + " " + (x));
            }
        }
    }
}