#!/bin/python3

import sys

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

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