#!/bin/python3

import sys

def sumOfGroup(k):
    # Return the sum of the elements of the k'th group.
    l =[]
    for i in range(1,1000000, 2):
        l.append(i)
    n = k * (k+1)
    n = int(n/2)
    sum=0
    #print(n)
    #no = sum(l[n-k:n+1])
    for j in range(1,k+1):
        #print(l[n])
        sum = sum+l[n-1]
        n=n-1
    print(sum)

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