#!/bin/python

import sys


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

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