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 is_prime(int n)
{
    int i;

    if (n % 2 == 0){
        return (0);
    }
    for (i = 3; i * i <= n; i += 2){
        if (n % i == 0){
            return (0);
        }
    }

    return (1);
}

int main(void)
{
    int n;
    int i;

    while (scanf("%d", &n) * n != 0){
        i = n;
        while (is_prime(i) != 1 || is_prime(i - 2) != 1){
            i--;
        }
        printf("%d %d\n", i - 2, i);
    }

    return (0);
}