#!/bin/python

import sys

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

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