#!/bin/python3

import sys

def sumOfGroup(k):
    h=1
    sum=0
    for i in range(k):
        for j in range(i):
            h=h+2
     
    for v in range(k):
        sum=sum+h
        h=h+2
        
    return sum
        
        

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