#!/bin/python3

import sys

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

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