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>

using namespace std;

const int MAX_P = 10020;
bool prime[MAX_P];

void init()
{
    for (int i = 0; i < MAX_P; i++)
        prime[i] = true;
    prime[0] = prime[1] = false;

    for (int i = 2; i * i < MAX_P; i++)
        if (prime[i]) 
            for (int j = 2 * i; j < MAX_P; j += i)
                prime[j] = false;
}


int main()
{
    init();

    int n;
    while (cin >> n) {
        while (n - 2 >= 0) {
            if (prime[n] && prime[n - 2]) {
                cout << n - 2 << " " << n << endl;
                break;
            }
            n--;
        }
    }

    return 0;
}