#!/bin/python3

import sys

def sumOfGroup(k):
    start = int(k * (k-1)/2) + 1
    end = int(k * (k+1)/2)
    start_val, end_val = 2 * start - 1, 2 * end - 1
    return int((start_val + end_val)/2) * (end - start + 1) 

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