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#include <iostream>
using namespace std;

int main()
{
	int n,r;
	cin >> n;
	if (n == 0 or n == 1)
	{
		r = 0;
	}
	if (n % 2 == 0)
	{
		r =n/ 2;
	}
	else if (n!=1)
	{
		r = n;
	}
	cout << r;
}