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 JAVA (judge verdict: Accepted)

import java.util.*;

public class Main{
    private static boolean isPrime(int x){
        if(x == 0 || x == 1) return false;
        for(int i = 2; i * i <= x; i++){
            if(x % i == 0){
                return false;
            }
        }
        return true;
    }

    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);

        while(true){
            int n = sc.nextInt();
            if(n == 0) break;

            for(int i = n; ; i--){
                if(isPrime(i) && isPrime(i - 2)){
                    System.out.println((i - 2) + " " + i);
                    break;
                }
            }
        }
    }
}