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.Scanner;

public class Main {

	static boolean[] primes;

	static void primeSet(final int MAX){
		primes = new boolean[MAX+1];

		primes[2] = true;
		for(int i=3;i<=MAX;i+=2){
			primes[i] = true;
		}
		int rt = (int) Math.sqrt(MAX);
		for(int i=3;i<=rt;i+=2){
			if(primes[i]){
				for(int j=i*2;j<=MAX;j+=i){
					primes[j] = false;
				}
			}
		}
	}

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

		while(true){
			int max = 0;
			int n = stdIn.nextInt();

			if(max<n){
				primeSet(n);
				max=n;
			}
			
			if(n==0){
				break;
			}

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