#!/bin/python3

import sys

def sumOfGroup(k):
    n=k*k-k+1
    sum1=n
    for i in range(k-1):
        n=n+2
        sum1=sum1+n
    return sum1
    
    # Return the sum of the elements of the k'th group.
    

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