Problem:
Score : 100 points

Problem Statement

How many ways are there to choose two distinct positive integers totaling N, disregarding the order?

Constraints

1 \leq N \leq 10^6

N is an integer.

Input

Input is given from Standard Input in the following format:

N

Output

Print the answer.

Sample Input 1

4

Sample Output 1

1

There is only one way to choose two distinct integers totaling 4: to choose 1 and 3. (Choosing 3 and 1 is not considered different from this.)

Sample Input 2

999999

Sample Output 2

499999

Solution in Java8 (OpenJDK 1.8.0) (judge verdict: Runtime Error)

import java.lang.reflect.Array;
import java.util.Arrays;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] d = new int[n];
        int[] cnt = new int[n];

        for (int i = 0; i < n; i++) {
            d[i] = sc.nextInt();
            cnt[d[i]]++;
        }

        Arrays.sort(d);

        long ans = 1;
        if (d[0] != 0 || cnt[0] != 1) {
            System.out.println(0);
            sc.close();
            return;
        } else {
            for (int i = 1; i < n; i++) {
                for (int j = 0; j < cnt[i]; j++) {
                    ans *= cnt[i - 1];
                    ans %= 998244353;
                }
            }
        }

        System.out.println(ans);
        sc.close();
    }
}