#!/bin/python3

import sys

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

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