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: Time Limit Exceeded)

#include<stdio.h>
void twin_prime(int n) {
	int a[10000],i,j,k=0,flag1,flag2;

	for (i = 3; i <=n; i+=2) {
		flag1 = 0;
		for (j = 3; j <=n; j++) {
			if (i != j && i%j == 0)
				flag1 = 1;
		}
		if (flag1 == 0)
			a[k++] = i;
	}
	for (i = k; i >= 0; i--) {
		flag2 = 0;
		for (j = k - 1; j >= 0; j--) {
			if (a[i] - a[j] == 2) {
				flag2 = 1;
				break;
			}
		}
		if (flag2)break;
	}
	printf("%d %d\n",a[j],a[i]);
	return;
}

int main(void) {
	int n;

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