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>

int isprime(int n);

int main(void)
{
	int i,n;

	while(scanf("%d",&n)!=0){
		for(i=n; i>=2; i--)
			if(isprime(i) && isprime(i-2)){
				printf("%d %d\n",i-2,i);
				break;
			}
	}

	return 0;
}

int isprime(int n)
{
	int i;

	if(n<=1)
		return 0;
	for(i=2; i*i<=n; i++)
		if(n%i==0)
			return 0;
	return 1;
}