#!/bin/python

import sys

def sumOfGroup(k):
    # list of elements the k'th group.
    elem = []
    start_element = k * (k-1) + 1
    sum_total = start_element
    if k == 1:
        return 1
    else:
        for x in xrange(1, k):
            sum_total = sum_total + start_element + 2
            start_element = start_element + 2
        return sum_total
                   
if __name__ == "__main__":
    k = int(raw_input().strip())
    answer = sumOfGroup(k)
    print answer