#!/bin/python3

import sys

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

    return ksum

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