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

int main(){
	int n,i,k=0;
	int max = 0;
	int cnt = 0;
	while(1){
		scanf("%d",&n);
		if(n == 0){
			break;
		}
		for(i = 0;i < n-2;i++){
			if(isprime(i)==1 && isprime(i+2)==1 && i>max){
				max = i;
			}
		}
		printf("%d %d\n",max,max+2);
		max = 0;

	/*
		for(k = 0;k < cnt;k++){
			if(prime_num[k] > max){
				max = prime_num[k];
			}
			prime_num[k] = 0;
		}
	*/
	}
	
	return 0;
}