Codeforces Calculating Function 486A

A solution in c++

#include<bits/stdc++.h>

#include<cstdio>

#include<cstring>

#include<cmath>

#include<algorithm>

using namespace std;

int main()

{

   long long int a, b, ck1=0,i,j,sum=0,sum1=0;

   scanf("%lld",&a);

   if(a%2==0){

     ck1 = a/2;

    printf("%lld\n", ck1);

   }

   else{

    ck1 = (((a/2)+1)*(-1));

     printf("%lld\n", ck1);

   }

}