View Code of Problem 18

#include<iostream>
#include<string>
#include<cmath>
#include<algorithm>
#include<vector>
#include<stack>
using namespace std;

int main()
{
	int i, j, k, flag;
	int n, m, t;
	string str, s;
	int sum;
	while (scanf("%d", &n) != EOF)
	{
		int sum = 0;
		int k = ceil((double)n / 2);
		for (i = 1; i < k; ++i)
			sum += 2 * i;
		if (n % 2 != 0)
			sum -= (k - 1);
		cout << sum << endl;
	}
	return 0;
}