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*i<=n;i++){
        if(n%i==0) return 0;
    }
    return 1;
}

int main(){
    int n,i,max=0,max2;
    while(1){
    scanf("%d",&n);
    for(i=n;i>0;i--){
        if(isprime(i)==1){
            if(isprime(i-2)==1){
                max=i;
                break;
            }
        }
    }
    if(n==0){
        break;
    }
    max2=max-2;
    printf("%d %d\n",max2,max);
    }
    return 0;
}