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 Java7 (OpenJDK 1.7.0) (judge verdict: Runtime Error)

import java.util.ArrayList;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		ArrayList<Integer> Ai = new ArrayList<Integer>();
		ArrayList<Integer> Bi = new ArrayList<Integer>();
		Scanner sc = new Scanner(System.in);
		
		int N = sc.nextInt(10);
		int i = 0;
		while(N!=i) {
			i++;
			Ai.add(sc.nextInt(10));
		}
		i=0;
		while(N!=i) {
			i++;
			Bi.add(sc.nextInt(10));
		}
		i = 0;
		int tmp1,tmp2,nb;
		while(N-1!=i) {
			i++;
			nb=1;
			while(nb!=N) {
			if(Ai.get(nb-1)>Ai.get(nb)) {
				tmp1 = Ai.get(nb-1);
				tmp2 =Ai.get(nb);
				Ai.set(nb, tmp1);
				Ai.set(nb-1, tmp2);
			}nb++;
			}
			
		}
		i=0;
		while(N-1!=i) {
			i++;
			nb=1;
			while(nb!=N) {
			if(Bi.get(nb-1)>Bi.get(nb)) {
				tmp1 = Bi.get(nb-1);
				tmp2 =Bi.get(nb);
				Bi.set(nb, tmp1);
				Bi.set(nb-1, tmp2);
			}nb++;
			}
			
		}
		i=0;
		while(N!=i) {
			if(Ai.get(i)>Bi.get(i)) {
				System.out.println("yes");
              break;
			}
			i++;
		}
      System.out.println("no");
	}
}