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 <iostream>
#include <cstdio>
#include <algorithm>
#include <cmath>
using namespace std;

bool isPrime(int n)
{
	if (n % 2 == 0) return false;
	for (int i = 3; i < n; i += 2){
		if (n % i == 0) return false;
	}
	return true;
}

int main(void)
{
	int n;
	while (scanf("%d", &n), n){
		
		for (int i = n; 5 <= i; i--){
			// cout << i << endl;
			if (isPrime(i) && isPrime(i-2)){
				cout << i-2 << " " << i << endl;
				break;
			}
		}
		
	}
	
	return 0;
}