Poj Solution 2909

http://poj.org/problem?id=2909

//* @author ������<hongxp11@163.com>
import java.util.Scanner;

public class Main {
 public static boolean isPrime(int n) {
    int root = (int) Math.sqrt(n);
    for (int i = 2; i <= root; i++) {
        if (n % i == 0)
            return false;
    }
    return true;
}

public static void main(String[] args) {
    Scanner in = new Scanner(System.in);
    int n;
    while ((n = in.nextInt()) != 0) {
        if(n == 4)
        {
            System.out.println(1);
            continue;
        }
        int count = 0;
        for (int i = 3; i <= n / 2; i+=2) {
            if (isPrime(i) && isPrime(n - i)) {
                count ++;
            }
        }
        System.out.println(count);
    }
  }
}