#!/bin/python3

import sys

def sumOfGroup(k):
    su=0
    final=0
    for i in range(1, k+1):
        su += i
    for n in range(su-k+1, su+1):
        final += ((2*n)-1)
    return final

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