#!/bin/python3

import sys

def sumOfGroup(k):
    # Return the sum of the elements of the k'th group.
    n = k * (k - 1) // 2 + 1
    odds = (n - 1) * 2 + 1
    odde = odds + (k - 1) * 2
    total = (odds + odde) * k // 2
    return total

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