[Codeforces] 486A - Calculating Function (Java)

https://codeforces.com/problemset/problem/486/A

Solution

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Solution {
    static long f(long n) {
        long answer = 0;
        if (n % 2 == 0) {
            answer = n / 2;
        } else { // sigma
            answer = (-1) * (n / 2 + 1);
        }
        return answer;
    }

    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        long n = Long.parseLong(br.readLine());
        System.out.print(f(n));
        br.close();
    }
}