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 C (judge verdict: Wrong Answer)

#include<math.h>
#include<stdio.h>
void twin_prime(int n) {
	int prime1[10000], prime2[10000];
	int i, j, k = 0, flag, b;

	for (i = 0; i <= n; i++)prime1[i] = 1;
	for (i = 4; i <= n; i += 2)prime1[i] = 0;

	b = sqrt(n);
	for (i = 3; i <= b; i += 2) {
		if (prime1[i]) {
			for (j = 2 * i; j < n; j += i)prime1[j] = 0;
		}
	}
	for (i = 2; i <= n; i++) 
		if (prime1[i]) prime2[k++] = i;
	
	for (i = k; i >= 0; i--) {
		flag = 0;
		for (j = k - 1; j >= 0; j--) {
			if (prime2[i] - prime2[j] == 2) {
				flag = 1;
				break;
			}
		}
		if (flag)break;
	}
	printf("%d %d\n", prime2[j], prime2[i]);
	return;
}

int main(void) {
	int n;

	while (1) {
		scanf("%d", &n);
		if (n == 0)break;
		twin_prime(n);
	}
	return 0;
}