#!/bin/python3

import sys

def sumOfGroup(k):
    # Return the sum of the elements of the k'th group.
    first_odd = ((k-1)*(k)//2)*2+1
    result = ((first_odd) + first_odd +2*(k-1))*k//2
    return(result)

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