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 <iostream>
using namespace std;
bool so[10000]={};

int main(){
  so[0] = 1;
  so[1] = 1;
  for(int i=2;i*i<=10000;i++)
    if(so[i] == 0)
      for(int j=2;j*i<=10000;j++)
	so[i*j] =1;
  int n;
  while(cin>>n && n){
    for(int i=n;i>=5;i--)
      if(so[i]==0 && so[i-2]==0){
	cout << i-2 <<" "<< i<<endl;
	break;
      }
  }

  return 0;
}