224. Boxes with Shells. Shells for six-inch howitzers were packed in boxes of 15, 18, and 20.

- Why do you have different boxes? - I asked the officer at the warehouse.
- You see, - he replied, - this allows us to deliver the required number of shells to the battery without opening the boxes.

Indeed, this system worked flawlessly when a large number of shells was needed, but it proved to be useless if, for example, 5, 10, 25, or 61 shells were required.

What is the largest number of shells that cannot be delivered to the battery in whole boxes, containing 15, 18, and 20 shells each? It is not too large.