#!/bin/python3

import sys

def sumOfGroup(k):
    first = k*(k-1)+1
    c=0
    for i in range(k):
        c+=first
        first+=2
    return c
        
    # Return the sum of the elements of the k'th group.

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