/* fibonacci sequence */
/**
 * fib(n): calculate the fibonacci sequence.
 * @input n the number to calculate fibonacci for
 * @result the value of the fibonacci sequence for the number
 */
fib = { n in
  if n == 0 // if n is zero, return zero
    then 0
  else if n == 1 // if n is one, return one
    then 1
  else fib(n - 1) + fib(n - 2)
}

// result of fib(20)
result = fib(20)
println(result)