#!/bin/python3

import sys

def sumOfGroup(k):
    # Return the sum of the elements of the k'th group.
    sum = 0
    ans = 0
    for i in range(0,k):
        sum += i
    
    odd_number = sum*2 + 1
   
    number = odd_number
    for j in range(0,k):   
        ans += number        
        number = number + 2
        
    return ans

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