procedure main()
    longest(".")   # needs a single character seed to throw away
end

procedure longest(Longest)
    Line := read() | return Longest        # read until we can return the longest strings
    if Line[*Longest] then Longest := Line # prime/reset Longest
    Longest := longest(Longest)            # use stack to hold multiples
    if Line[*Longest] then write(Line)     # write only longest strings,
                                           # Line must be at least as long as Longest
    return Longest                         # feed back longest for length
end