Beaches are filled with sand, water, fish, and sun. Given a string, calculate how many times the words `"Sand"`, `"Water"`, `"Fish"`, and `"Sun"` appear without overlapping (regardless of the case).

## Examples

```python
sum_of_a_beach("WAtErSlIde")                    ==>  1
sum_of_a_beach("GolDeNSanDyWateRyBeaChSuNN")    ==>  3
sum_of_a_beach("gOfIshsunesunFiSh")             ==>  4
sum_of_a_beach("cItYTowNcARShoW")               ==>  0
```