#!/bin/python3

import sys

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

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