#!/bin/python

import sys
def sumOfGroup(k):
    sumof = 0
    start_num = 2*k+1
    for i in range(0,k):
        sumof = sumof + start_num 
        start_num = start_num + 2
    return sumof 
        

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