#!/bin/python3

import sys

def sumOfGroup(k):
    # Return the sum of the elements of the k'th group.
    element = (k*(k+1)//2)
    n = (2 * (element))-1;
    u = (2 * ((element-k))+1)
    #print(element, n,u)
    s = 0
    for i in range(u,n+1) :
        if i%2!=0:
            s+=i
        #print(i)
    return s

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