#!/bin/python3

import sys

def sumOfGroup(k):
    SumofK = ((k)*(k-1))//2
    count = 0
    for i in range(k):
        count = count+2*(SumofK+i)+1;
    return count
if __name__ == "__main__":
    k = int(input().strip())
    answer = sumOfGroup(k)
    print(answer)