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 prime(int n){
  int i;
  for(i = 2;i*i <= n;i++){
    if(n % i == 0){
      return 0;
    }
  }
  return 1;
}
int main(){
  int n, i;
  scanf("%d", &n);
  while(n != 0){
    for(i = n;i > 0;i--){
      if(prime(i)){
        if(prime(i-2)){
          printf("%d %d\n", i-2, i);
          break;
        }
      }
    }
    scanf("%d", &n);
  }
  return 0;
}