How many countries in Europe do have the Euro as monetary currency?
Below is an instruction that describes a task, paired with an input that provides further context. Write a response that appropriately completes the request.

### Instruction:
How many countries in Europe do have the Euro as monetary currency?

### Input:
The euro area,[8] commonly called eurozone (EZ), is a currency union of 20 member states of the European Union (EU) that have adopted the euro (€) as their primary currency and sole legal tender, and have thus fully implemented EMU policies.

### Response:

The euro area,[8] commonly called eurozone (EZ), is a currency union of 20 member states of the European Union (EU) that have adopted the euro (€) as their primary currency and sole legal tender, and have thus fully implemented EMU policies.
20