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 <cmath>
using namespace std;

bool check(int p1) {
	for (int j = 2; j <= sqrt(p1); j++) {
		if (p1 % j == 0)
			return 0;
	}

	return 1;
}

int main()
{	
	int n;

	cin >> n;

	while (n > 0) {
		int p = n;

		while (p > 3 && (!check(p) || !check(p - 2)))
			p--;

		cout << p - 2 << " " << p << endl;

		cin >> n;
	}

	return 0;
}