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 Scala (judge verdict: Accepted)

import java.util.Scanner

object Main {
  def isPrime(p: Int) = if (p == 1) {
    false
  } else {
    (2 to math.sqrt(p).toInt).forall(p % _ != 0)
  }

  def main(args: Array[String]): Unit = {
    val sc: Scanner = new Scanner(System.in)
    while (sc.hasNext()) {
      val n: Int = sc.nextInt
      var ans = 0
      for (i <- 1 to n) {
        if (isPrime(i) && isPrime(n - i + 1)) {
          ans += 1
        }
      }
      println(ans)
    }
  }
}