#include <iostream>
#include <fstream>
using namespace std;

int main()
{
	ifstream inFile("fractii.in");
	ofstream outFile("fractii.out");
	int n;
	int count = 0;

	inFile >> n;

	for (int i = 1; i <= n; i++)
	{
		if (i == 1)
			++count;
		
		for (int j = 1; j <= n; j++)
		{
			if (i == j)
				continue;

			if (i % 2 != 0)
			{
				++count;
			}

			else
			{
				if (j % 2 == 0)
					continue;
				++count;
			}
		}
	}

	outFile << count;
	outFile.flush();

	return 0;
}