Suppose: the crow's mouth length is L, the bottle length is A, the width is B and the height is C, then when the water reaches the height of C-L, the crow can drink water.

Then fill a bottle with stones and water whose length is A, width is B and height is C-L.. Let the water content be the least, let the stone

The content is the most. So first lay a layer of stones on the bottom of the bottle, the number is N, and then nd.

At the bottom of the bottle, when putting stones again, some stones will be put in the gap of the next layer of stones. The calculation result depends on the given data.

If you think the answer is too difficult, it can be simplified as: water can not be drunk until it reaches the bottle mouth, and stones can cover the bottom of the bottle, that is, ID = A, JD = B, KD = C.

Then the bottle volume ABC, stone volume 4/3 pay 3 * Ijk. The volume of water is equal to the volume of the bottle-the volume of the stone. So the water in the bottle arrived.

Effective when the volume of water is divided by the height of the bottom area!

Answer is over, don't ask questions!