digits = iter (n: int) yields (int)
    while n>0 do
        yield(n//10)
        n := n/10
    end
end digits

mdr = proc (n: int) returns (int,int)
    i: int := 0
    while n>=10 do
        m: int := 1
        for d: int in digits(n) do
            m := m * d
        end
        n := m
        i := i+1
    end
    return (i,n)
end mdr

first_mdr = iter (target_mdr, n: int) yields (int)
    i: int := 0
    while n>0 do
        x, m: int := mdr(i)
        if m=target_mdr then
            yield(i)
            n := n -1
        end
        i := i+1
    end
end first_mdr

start_up = proc ()
    po: stream := stream$primary_output()
    nums: sequence[int] := sequence[int]$[123321, 7739, 893, 899998]

    stream$putl(po, "  N     MDR  MP")
    stream$putl(po, "======  ===  ==")
    for num: int in sequence[int]$elements(nums) do
        stream$putright(po, int$unparse(num), 6)
        stream$puts(po, " ")
        i, m: int := mdr(num)
        stream$putright(po, int$unparse(m), 3)
        stream$puts(po, "  ")
        stream$putright(po, int$unparse(i), 3)
        stream$putl(po, "")
    end

    stream$putl(po, "\nMDR: [n0..n4]")
    stream$putl(po, "===  ========")
    for dgt: int in int$from_to(0,9) do
        stream$putright(po, int$unparse(dgt), 3)
        stream$puts(po, ": ")
        for num: int in first_mdr(dgt, 5) do
            stream$puts(po, int$unparse(num) || " ")
        end
        stream$putl(po, "")
    end
end start_up