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 JAVA (judge verdict: Accepted)

import java.util.Arrays;
import java.util.Scanner;

//Pair of Primes
public class Main{

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		boolean[] p = new boolean[10002];
		Arrays.fill(p, true);
		p[0] = p[1] = false;
		for(int i=2;i<=10001;i++){
			if(p[i]){
				for(int j=i*2;j<=10001;j+=i)p[j]=false;
			}
		}
		while(sc.hasNext()){
			int n = sc.nextInt();
			int c = 0;
			for(int i=1;i<=n;i++)if(p[i]&&p[n+1-i])c++;
			System.out.println(c);
		}
	}
}