#!/bin/python3

import sys

def sumOfGroup(k):
    # Return the sum of the elements of the k'th group.
    
    t = int(0.5 * k * (k + 1))
   

    
    return sum([2*x + 1 for x in list(range(t - k, t))])
    
    

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