How to know what item the user gave to the bot?

[SmallMarbles]

So, i wanted to make a shop bot.

Essentially, the user drops for example, 5 emeralds.

The bot gets these 5 emeralds, but how can i check if the user REALLY gave 5 emeralds and not 2 dirt blocks ( for example )?

And if it gets 5 emeralds, it drops the desired item.

[WhoTho]

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