active class Main
  def main(): unit
    let fib10 = this.fibonacci(10)
    let fib20 = this.fibonacci(20)
    println("fib(10) = {}", fib10)
    println("fib(20) = {}", fib20)
  end

  def fibonacci(n: int): int
    if n <= 1 then
      n
    else
      this.fibonacci(n - 1) + this.fibonacci(n - 2)
    end
  end
end