predicate knapsack(
	array[int] of int: w,
	array[int] of int:p, 
  array[int] of var int:x,
	var int: W, var int: P
) = 
	assert(
		index_set(w) = index_set(p) /\ index_set(w) = index_set(x),
		"index set of weights must be equal to index set of profits and index set of items",
	) /\ assert(
		lb_array(w) >= 0,
		"weights must be non-negative",
	) /\ assert(
		lb_array(p) >= 0,
		"profits must be non-negative",
	) /\ fzn_knapsack(w, p, x, W, P);