#!/bin/python3

import sys

def sumOfGroup(k):
    # Return the sum of the elements of the k'th group.
    s=0
    for i in range(((k-1)*(k))+1,((k-1)*(k)+(2*k+1)),2):
        s+=i
    return s
if __name__ == "__main__":
    k = int(input().strip())
    answer = sumOfGroup(k)
    print(answer)