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: Accepted)

#include <stdio.h>
int isprime(int n) { 
	for(int i=2;i*i<=n;i++) { 
		if(n%i==0)return 0; 
	} 
	return 1; 
}
int main() { 
	const int MAX_V=10000;
	int prime[MAX_V+1];
	int i,k,v,n,p1,q1; 
	for(i=2;i<=MAX_V;i++) { 
		prime[i]=isprime(i);
	}  
	while(1) { 
		scanf("%d",&n);
		if(n==0)break;
		for(i=2;i<=n;i++){
			if(prime[i-2] && prime[i]){
				p1=i-2;
				q1=i;
			}
		}
		printf("%d %d\n",p1,q1);
	} 
	return 0; 
}