proc{Bridge J A B C D}
   local L4 in
      fun{L4 L}
     case L
     of H1|H2|H3|H4|T then H1|{L4 T}
     else
        nil
     end
      end
      A = {L4 J}
      case J
      of H|T then B = {L4 T}
     case T of H1|T1 then C = {L4 T1}
        case T1 of H2|T2 then D = {L4 T2}
        else D = nil
        end
     else C = nil D = nil
     end
      else B = nil C = nil D =nil
      end
   end
end