#!/bin/python3

import sys

def sumOfGroup(k):
    sum1=0
    for i in range(k*(k-1)+1,k*(k+1)):
        if i%2!=0:
            sum1+=i;
    return sum1        
            # Return the sum of the elements of the k'th group.

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