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: Runtime Error)

#include<stdio.h>
#include<math.h>

int	Prime(int	x){
	int	n;
	if(x	==	2)return	1;
	if(x	<	2	||	x	%	2	==	0)return	0;
	for(n	=	3;	n	<=	sqrt((double)x);	n	+=	2){
		if(x	%	n	==	0)return	0;
	}
	return	1;
}

int	main(){
	int	n,	i,	cnt	=	0,	max	=	0,	data[100001];
	while(1){
	  scanf("%d",	&n);
	  if(n==0) break;
	  for(i	=	0;	i	<=	n;	i++){
		  if(Prime(i)	==	1){
			  data[cnt]	=	i;
			  cnt++;
		  }	
		}
		for(i	=	1;	i	<=	cnt;	i++){
			if(data[i]	-	data[i	-	1]	==	2)max	=	i;
		}
		if(max	!=	0)printf("%d %d\n",	data[max - 1],	data[max]);
	}
	return	0;
}