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>
#define MAX_V 10000

int main() {
	int prime[MAX_V + 1];
	int data[10000];
	int i, k, cnt = 0, n, p1, q1;
	for(i = 2; i <= MAX_V; i++) {
		prime[i] = 1;
	}
	for(i = 2; i * i <= MAX_V; i++) {
		if(prime[i]) {
			for(k = 2 * i; k <= MAX_V; k += i) {
				prime[k] = 0;
			}
		}
	}
	while(1) {
		scanf("%d", &n);
		if(n == 0) break;
		data[cnt] = n;
		cnt++;
	}
	for(i = 0; i < cnt; i++) {
		for(k = 5; k <= data[i]; k++) {
			if(prime[k] && prime[k-2]) {
				p1 = k - 2;
				q1 = k;
			}
		}
		printf("%d %d\n", p1, q1);
	}
	return 0;
}