#include <iostream>
using namespace  std;

int main()
{
	int summary = 0;
	int N;

	cout << "Enter the amount of elements(N) = ";
	cin >> N;

	for (int i = 0; i < N; i++)
	{
		if (i % 2 == 0)
			summary += i + 1;
		else
			summary += (i + 1) * (-1);
	}

	cout << "Summary of N elements = " << summary;

	return 0;
}