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){
    int i;
    for(i = 2;  i < n; i ++ ){
        if(n % i == 0)return 0;
    }
    return 1;
}
int main(void){
    const int NUM = 10001;
    int i,n,prime[NUM],p1,q1;
    for(i = 2; i < NUM; i ++ ){
        prime[i] = isprime(i);
    }
    
    while(1){
        scanf("%d",&n);
        if(n == 0)break;
        for(i = n; i >= 2; i --){
            if(prime[i] == 1 && prime[i - 2] == 1){
                    q1 = i;
                    p1 = i - 2;
                    printf("%d %d\n",p1,q1);
                    break;
            }
        }
    }
    return 0;
}