#include <iostream>
using namespace std;
int main() {
    int n,res=0;
    cin >> n;
    if (n < 0) {
        n = n*-1;
        int *arr;
        arr = new int[n+2];
        arr[0] = 1;
        for (int i = 1; i < n+2; i++) {
            arr[i] = arr[i - 1] - 1;
        }
        for (int i = 0; i < n+2; i++) {
            res = res + arr[i];
        }
        cout << res;
    }
    else if(){
        int *arr;
        arr = new int[n];
        arr[0] = 1;
        for (int i = 1; i < n; i++) {
            arr[i] = arr[i - 1] + 1;
        }
        for (int i = 0; i < n; i++) {
            res = res + arr[i];
        }
        cout << res;
    }
    return 0;
}

n = n*-1; ?
arr[i] = arr[i - 1] - 1; ?
-10000.....-1 0 1