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

int Judge(int n)
{
  int i;
  if(n<2)return 0;
  if(n==2)return 1;
  if(n%2==0)return 0;
  for(i=3;i<n;i+=2){
    if(n%i==0)return 0;
  }
  return 1;
}