#!/bin/python3

import sys

def sumOfGroup(k):
    n = k*(k-1)+1
    l=[]
    for i in range(1,k+1,1):
        l.append(n)
        n+=2
    sum1 = sum(l)
    return sum1

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