#!/bin/python3

import sys

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

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