#!/bin/python3

import sys

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

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