Problem:
Score : 100 points

Problem Statement

It is known that the area of a regular dodecagon inscribed in a circle of radius a is 3a^2.

Given an integer r, find the area of a regular dodecagon inscribed in a circle of radius r.

Constraints

1 \leq r \leq 100

r is an integer.

Input

Input is given from Standard Input in the following format:

r

Output

Print an integer representing the area of the regular dodecagon.

Sample Input 1

4

Sample Output 1

48

The area of the regular dodecagon is 3 \times 4^2 = 48.

Sample Input 2

15

Sample Output 2

675

Sample Input 3

80

Sample Output 3

19200

Solution in Ruby (2.3.3) (judge verdict: Runtime Error)

def method_name(n, ai)
  bi = Array.new(n, 0)
  n.downto(1) do |i|
    sum = (2*i).step(n, i).inject(0){|sum, j| sum += bi[j-1]}
    bi[i-1] = 1 if sum.odd? != ai[i-1].odd?
  end

  puts bi.inject(:+)
  bi.each_with_index{|v, k| puts k + 1 if v == 1}
end

n = gets.chomp.to_i
ai = gets.chomp.split.map(&:to_i)
method_name(n, ai)