// series 1 - 2 + 3 - 4 +......
#include <iostream>

using namespace std;
// Function to calculate sum

int solve_sum(int n)
{

// when n is odd

if (n % 2 == 1)

return (n + 1) / 2;

// when n is not odd

return -n / 2;
}
// Driver code

int main()
{

int n = 8;

cout << solve_sum(n);

return 0;
}