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.Arrays;
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		boolean[] isPrime = Sieve.isPrimeArray(10000);
		int[] max = new int[10001];
		int x = 0;
		for(int i=5;i<=10000;i++) {
			if (isPrime[i] && isPrime[i-2]) {
				x = i;
			}
			max[i] = x;
		}
		Scanner sc = new Scanner(System.in);
		while(true) {
			int n = sc.nextInt();
			if (n == 0) {
				break;
			}
			System.out.println((max[n]-2) + " " + max[n]);
		}
	}

}
class Sieve {
	public static boolean[] isPrimeArray(int max) {
		boolean[] isPrime = new boolean[max+1];
		Arrays.fill(isPrime, true);
		isPrime[0] = isPrime[1] = false;
		for(int i=2;i*i<=max;i++) {
			if (isPrime[i]) {
				int j = i * 2;
				while(j<=max) {
					isPrime[j] = false;
					j += i;
				}
			}
		}
		return isPrime;
	}
}