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.*;

class Main {
        public static void main(String args[]) {
                Scanner sc = new Scanner(System.in);
                boolean[] prime = new boolean[10001];
                prime[0] = prime[1] = true;
                for (int i = 2; i < 10001; i++) {
                        if (prime[i] == false) {
                                int j = 2;
                                while (i * j < 10001) {
                                        prime[i * j] = true;
                                        j++;
                                }
                        }
                }
                while (true) {
                        int N = sc.nextInt();
                        if (N == 0) {
                                return;
                        }
                        while (true) {
                                if (prime[N] == false && prime[N - 2] == false) {
                                        System.out.println(N-2 + " " + N);
                                        break;
                                }
                                N--;
                        }
                }
        }
}