#!/bin/python3

import sys

def sumOfGroup(k):
    # Return the sum of the elements of the k'th group.
    a=k*(k-1)+1
    ans=0
    while(k):
        ans+=a
        a+=2
        k=k-1
    return ans
    

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