program hailstone_sequence;
    hail27 := hailstone(27);
    print("The hailstone sequence for the number 27 has", #hail27, "elements,");
    print("starting with", hail27(..4), "and ending with", hail27(#hail27-3..));

    sizes := [#hailstone(n) : n in [1..99999]];
    maxsize := max/sizes;
    maxelem := [n : n in [1..#sizes] | sizes(n) = maxsize](1);

    print("The number < 100,000 with the longest hailstone sequence is",maxelem);
    print("The length of its sequence is",sizes(maxelem));

    proc hailstone(n);
        seq := [];
        loop doing seq with:= n; while n/=1 do
            if even n then
                n div:= 2;
            else
                n := 3*n + 1;
            end if;
        end loop;
        return seq;
    end proc;
end program;