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>
#include <math.h>

int sosu(int k);

int main(void){

	int n;
	int i;
	int p1 = 3;
	int q1 = 5;

	scanf("%d",&n);

	while(n != 0){
		for(i = 3; i+2<=n ; i+=2){
			if(sosu(i) == 1 && sosu(i+2) ==1){
				p1 = i;
				q1 = i+2;
			}
		}
		printf("%d %d\n",p1,q1);
		scanf("%d",&n);
	}

	return 0;
}

int sosu(int k){
	int i;

	if(k == 1){
		return 0;
	}else if(k == 2){
		return 1;
	}

	if(k % 2 == 0){
		return 0;
	}

	for(i=3;i <= sqrt(k);i+=2){
		if( k % i == 0 ){
			return 0;
		}
	}

	return 1;
}