fun factorial (n: int) : int = do
    match n with
        | 0 -> return 1
        | else return n * factorial(n - 1)
    end
end

fun also_factorial (n: int) : int = do
    if n == 0 then
        return 1
    else
        return n * also_factorial(n - 1)
    end
end

fun main : void = do
    let result : int = factorial(5)
    @write(result)
end