Problem:
Pair of Primes

We arrange the numbers between 1 and N (1 <= N <= 10000) in increasing
order and decreasing order like this:

1 2 3 4 5 6 7 8 9 . . . N
N . . . 9 8 7 6 5 4 3 2 1

Two numbers faced each other form a pair. Your task is to compute the number of pairs P such that both
numbers in the pairs are prime.

Input

Input contains several test cases. Each test case consists of an integer N in
one line.

Output

For each line of input, output P .

Sample Input

1
4
7
51

Output for the Sample Input

0
2
2
6

Solution in C++ (judge verdict: Time Limit Exceeded)

#include <iostream>

int main()
{
	bool ptable[10001] = {0};
	int n;
	
	ptable[0] = 1;
	ptable[1] = 1;
	ptable[2] = 0;
	
	for( int i = 3; i*i <= 10000; i++)
	{
		if( i % 2 == 0 )
			ptable[i] = 1;

		if( ptable[i] == 0 )
		{
			for( int j = 2 ; i*j <= 10000; j++ )
			{
				ptable[i*j] = 1;
			}
		}
	}
	
	while( std::cin >> n, n)
	{
		int count = 0;
		
		for(int i = 1; i <= n; i++)
		{
			if( ptable[i] == 0 && ptable[n-i+1] == 0)
				count++;
		}
		std::cout << count <<std::endl;
	}
	
	return 0;
}