#!/bin/python3

import sys

def sumOfGroup(k):
    # Return the sum of the elements of the k'th group.
    nb_elements = (k * (k+1)) // 2
    res = 0
    for i in range(1, k+1):
        res += (nb_elements - i) * 2
        res += 1
    return res

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