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 main()
{
    int i,j,p,n;
    int prime[10001]={0};

    while(scanf("%d",&n),n){

        for(i = 2;i < 10000;i++) prime[i]=1;

        for(i = 2;i <= n;i++) if(prime[i]) for(j=i+i;j<=n;j+=i) prime[j]=0;

        for(i=3;i<=n-2;i+=2) if(prime[i]) if(prime[i+2]) p=i;

        printf("%d %d\n",p,p+2);

    }   
    return 0;
}