#!/bin/ruby

def sumOfGroup(k)
    # Return the sum of the elements of the k'th group.
    p = k * (k - 1) / 2
    p = 2 * p + 1
    sum = 0
    for i in 0..k-1
        sum += p + 2 * i
    end
    return sum
end

k = gets.strip.to_i
answer = sumOfGroup(k)
puts answer