Do not drive children into the framework of

- You do not get - I said year-old son. - I assure you: you do not succeed, this figure in this cell is not suitable.
It was a question that's such a device.

Four figures: a disk, triangle, pentagon, flower. Respectively - four cells for them.
- You have a flower to another cell is not inserted, it is impossible - I repeated, trying to send a hand-year-old son.
Son did not listen. He did not know such a thing - it is impossible.
Decide the answer? - I asked.
Son, uttering short beeps, no answer.

It took a little more time, I walked away, the son was tired and went to bed.

Walking past, I suddenly noticed - he still put a flower.

"Old fart" - said in such cases, one of my intelligent repressed relative.

"Old fart" - I thought to myself.

I had forgotten how to do the impossible.

I learned how to put barriers to his son.