(knapsack=
  ( things
  =   (map.9.150.1)
      (compass.13.35.1)
      (water.153.200.2)
      (sandwich.50.60.2)
      (glucose.15.60.2)
      (tin.68.45.3)
      (banana.27.60.3)
      (apple.39.40.3)
      (cheese.23.30.1)
      (beer.52.10.3)
      (suntan cream.11.70.1)
      (camera.32.30.1)
      (T-shirt.24.15.2)
      (trousers.48.10.2)
      (umbrella.73.40.1)
      (waterproof trousers.42.70.1)
      (waterproof overclothes.43.75.1)
      (note-case.22.80.1)
      (sunglasses.7.20.1)
      (towel.18.12.2)
      (socks.4.50.1)
      (book.30.10.2)
  )
& 0:?maxvalue
& :?sack
& ( add
  =     cumwght
        cumvalue
        cumsack
        name
        wght
        val
        pcs
        tings
        n
        ncumwght
        ncumvalue
    .     !arg
        : ( ?cumwght
          . ?cumvalue
          . ?cumsack
          . (?name.?wght.?val.?pcs) ?tings
          )
      & -1:?n
      &   whl
        ' ( 1+!n:~>!pcs:?n
          & !cumwght+!n*!wght:~>400:?ncumwght
          & !cumvalue+!n*!val:?ncumvalue
          & (   !tings:
              & (   !ncumvalue:>!maxvalue:?maxvalue
                  &     !cumsack
                        ( !n:0&
                        | (!n.!name)
                        )
                    : ?sack
                |
                )
            |   add
              $ ( !ncumwght
                . !ncumvalue
                .   !cumsack
                    (!n:0&|(!n.!name))
                . !tings
                )
            )
          )
  )
& add$(0.0..!things)
& out$(!maxvalue.!sack)
);

!knapsack;