#!/bin/python3

import sys

def sumOfGroup(k):
    l=[]
    a=0
    sum=0
    y=1
    while(len(l)<=k):
        a=a+1
        l1=[]
        for i in range(y,1000000000000000000000,2):
            l1.append(i)
            if(len(l1)==a):
                break
        y=i+2 
        l.append(l1)
    for x in range(0,len(l))  :
        if((k-1)==x):
            for y in range(0,len(l[x])):
                sum=sum+l[x][y]
    return sum        
            
            
        
        

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