#!/bin/python3

import sys

def sumOfGroup(k):
    start = (k*(k-1)) + 1
    sum = 0
    count = 0
    num = start
    while(count!=k):
        if(num%2 == 1):
            sum += num
            num += 2
            count += 1
    return(sum)

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