#!/bin/python3

import sys

def sumOfGroup(k):
    # Return the sum of the elements of the k'th group.
    first=(k-1)**2+k
    sum1=0
    for i in range(0,k):
        sum1+=first
        first+=2
    return sum1

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