#!/bin/python3

import sys

def sumOfGroup(k):
    # Return the sum of the elements of the k'th group.
    if k ==1:
        return 1
    if k ==2:
        return 8
    idx = 1
    sum = 0
    #j = 1
    temp = (k * k) - k + 1
    sum = temp
    for i in range(1,k):
        temp += 2
        sum += temp
    return int(sum)    

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