#include <iostream>

using namespace std;

int main(){
    int N;
    cin >> N;

    int start = 1;
    int end = N;

    int ans = 0;

    for(int i = 0; i < N/2; i++){
        if(start == end) break;
        int tmp = (end*start) + (start - end);
        end--;
        int tmp2 = (end*start) + (end - start);
        start++;
        ans += (tmp+tmp2);
    }
        
    cout << ans << endl;
    return 0;
}