#!/bin/python3

import sys

def sumOfGroup(k):
    num=k**2 - (k-1);
    sum=0
    for i in range(k):
        sum=sum+num
        num=num+2
    return sum    

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