Given a nonempty finite list of integers, output a *truthy* value if there are exactly two equal entries and all other entries are distinct, and a *falsey* value otherwise.

### Examples

```
truthy:
[1,1]
[1,2,1]
[1,6,3,4,4,7,9]

falsey:
[0]
[1,1,1]
[1,1,1,2]
[1,1,2,2]
[2,1,2,1,2]
[1,2,3,4,5]

```