#!/bin/python

import sys

def sumOfGroup(k):
    # Return the sum of the elements of the k'th group.
    list_odd=[]
    num_odd=k*(k-1)+1
    for num in range(0,k):
        list_odd.append(num_odd)
        num_odd=num_odd+2
    return sum(list_odd)
        

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