#!/bin/python3

import sys

def sumOfGroup(k):
    # Return the sum of the elements of the k'th group.
    no=k*(k-1)+1
    x=[]
    for i in range(k):
        x.append(no)
        no=no+2
    return sum(x)
     

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