#!/bin/python3

import sys

def sumOfGroup(k):
    
    
    x=(k*(k-1))+1
    #print(x)
    my_sum=0
    for i in range(x,x+((k-1)*2)+1,2):
        my_sum+=i
        
    return my_sum
    # Return the sum of the elements of the k'th group.

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