#!/bin/python3


import sys

def sumOfGroup(k):
    b, t, i, y, Sum = [], True, 1, (k-1)*(k) / 2, 0
    # Return the sum of the elements of the k'th group.
    y=int(y)
    while t == True:
        if i==1 or i%2!=0:
            b.append(i)
        if len(b) >= (y + k):
            t = False
        i += 1
        
    for t in range(y, y + k):
        Sum = Sum + b[t]
    return Sum


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