When passing STACK_LENGTH to Fisherman's Gambit II, rather than a proper mishap it raises an IndexOutOfBounds exception cause stack.getPositiveIntUnderInclusive(stack.lastIndex, stack.size - 1) should be stack.getPositiveIntUnderInclusive(stack.lastIndex, stack.size - 2), since the following line stack.removeLast() reduces the stacksize and thus the acceptable range of values.