#!/bin/python3

import sys

def sumOfGroup(k):
    sum = 0
    l = int((k-1)*(k)/2)
    s = 2*(l-1)+1
    for i in range(k):
        sum = sum + s + 2 + 2*i 
    return sum    
        
    # Return the sum of the elements of the k'th group.

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