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: Time Limit Exceeded)

#include<stdio.h>

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

int main() {
  int k, i, n, flg, data[10000] = {0};
  while(1) {
    scanf("%d", &n);
    if(n == 0) break;
    k = 0;
    for(i = n; i >= 3; i--) {
      flg = isprime(i);
      if(flg == 1) {
        data[k] = i;
        if(data[k - 1] - data[k] == 2) break;
        k++;
      }
    }
    printf("%d %d\n", data[k], data[k - 1]);
  }
  return 0;
}