Problem:
Score : 100 points

Problem Statement

You are given a positive integer N.
Find the minimum positive integer divisible by both 2 and N.

Constraints

1 \leq N \leq 10^9

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N

Output

Print the minimum positive integer divisible by both 2 and N.

Sample Input 1

3

Sample Output 1

6

6 is divisible by both 2 and 3.
Also, there is no positive integer less than 6 that is divisible by both 2 and 3.
Thus, the answer is 6.

Sample Input 2

10

Sample Output 2

10

Sample Input 3

999999999

Sample Output 3

1999999998

Solution in C++14 (GCC 5.4.1) (judge verdict: Wrong Answer)


//#include <bits/stdc++.h>
#include <iostream>
#include <algorithm>
#include <string>
#include <vector>
using namespace std;
int n;

int main(){
  cin >> n;
  vector<int> A;
  vector<int> num;
  int sum = 0;
  int x;
  int b;
  for(int i = 0; i < n; i++){
    cin >> x;
    A.push_back(x);
    num.push_back(x - (i + 1));
  }
  sort(num.begin(),num.end());
  if(num.size() % 2 == 1) b = num[num.size()/2];
  else b = ( num[num.size()/2] + num[num.size()/2 - 1] ) / 2;

  int res = 0;
  for(int i = 0; i < n; i++){
    res +=  abs( A[i] - ( b + i+1));
  }

  cout <<  res << endl;



  return 0;
}