#!/bin/python3

import sys

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

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