#!/bin/python3

import sys

def sumOfGroup(k):
    _sum = 0
    for i in range(k*k-k+1, (k+1)*(k+1)-k, 2) :
        _sum +=i
    return _sum

if __name__ == "__main__":
    k = int(input().strip())
    answer = sumOfGroup(k)
    print(answer)