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 {
	static Scanner sc = new Scanner(System.in);
	static int[]prime;
	static int n;
	public static void main(String[] args) {
		makePrime();
		while(read()){
			solve();
		}
	}
	static boolean read(){
		n = sc.nextInt();
		if(n == 0)return false;
		return true;
	}
	static void solve(){
		int p = 0, q = 0;
		for(int i = 3; i <= n; i++){
			if(prime[i] == 1 && prime[i - 2] == 1){
				p = Math.max(p, i - 2);
				q = Math.max(q, i);
			}
		}
		System.out.print(p + " " + q);
		System.out.println();
	}
	static void makePrime(){
		prime = new int[10000+1];
		for(int i = 1; i < prime.length; i++)
			prime[i] = 1;
		for(int i = 2; i < prime.length; i++){
			if(prime[ i ] == 1){
				for(int j = i; i*j < prime.length; j++)
				prime[ i*j ] = 0;
			}
		}
	}
}