#!/bin/python3
import sys
sys.setrecursionlimit(1500000)
def sum_to(n):
    sum_=0
    for i in range(n+1):
        sum_+=i
    return sum_

def sumOfGroup(k):
    start=2*sum_to(k-1)+1
    end=2*sum_to(k)-1
    sum_=0
    for i in range(start,end+1):
        if(i%2==1):
            sum_+=i
    return sum_
    

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