(knapsack=
  ( things
  =   (map.9.150)
      (compass.13.35)
      (water.153.200)
      (sandwich.50.160)
      (glucose.15.60)
      (tin.68.45)
      (banana.27.60)
      (apple.39.40)
      (cheese.23.30)
      (beer.52.10)
      ("suntan cream".11.70)
      (camera.32.30)
      (T-shirt.24.15)
      (trousers.48.10)
      (umbrella.73.40)
      ("waterproof trousers".42.70)
      ("waterproof overclothes".43.75)
      (note-case.22.80)
      (sunglasses.7.20)
      (towel.18.12)
      (socks.4.50)
      (book.30.10)
  )
& 0:?maxvalue
& :?sack
& ( add
  =     cumwght
        cumvalue
        cumsack
        name
        wght
        val
        tings
        n
        ncumwght
        ncumvalue
    .     !arg
        : (?cumwght.?cumvalue.?cumsack.(?name.?wght.?val) ?tings)
      & -1:?n
      &   whl
        ' ( 1+!n:~>1:?n
          & !cumwght+!n*!wght:~>400:?ncumwght
          & !cumvalue+!n*!val:?ncumvalue
          & (   !tings:
              & (   !ncumvalue:>!maxvalue:?maxvalue
                  &     !cumsack
                        (!n:0&|!name)
                    : ?sack
                |
                )
            |   add
              $ ( !ncumwght
                . !ncumvalue
                .   !cumsack
                    (!n:0&|!name)
                . !tings
                )
            )
          )
  )
& add$(0.0..!things)
& out$(!maxvalue.!sack));

!knapsack;