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(void)
{
	int n;
	int flg[10001];
	int i,j;
	int p1,q1;
	
	scanf("%d",&n);
	while(n!=0){
		for(i=2;i<=n;i++){
			flg[i]=0;
		}
		for(i=2;i*i<=n;i++){
			if(flg[i]==0){
				for(j=2;i*j<=n;j++){
					flg[i*j]=1;
				}
			}
		}
		for(i=2;i<=n;i++){
			if(flg[i]==0 && flg[i-2]==0){
				p1=i-2;
				q1=i;
			}
		}
		printf("%d %d\n",p1,q1);
		scanf("%d",&n);
	}
	return 0;
}