#!/bin/python3

import sys

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

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