#!/bin/python3

import sys

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

    return total

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