#!/bin/python3

import sys

def sumOfGroup(k):
    a=k**2-k+1
    l=[a]
    for _ in range(k-1):
        l.append(a+2)
        a=a+2
    
    return sum(l)

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