I have a csv file which has three columns (A, B, and C) and their values are like the below figure:
[CSV Table](https://i.stack.imgur.com/isvMl.png)

```
1,2,4
1,257,5
1,258,6
1,8,7
1,260,8
2,24,9
2,26,10
2,234,11
3,14,12
3,22,13
3,78,14

```

I want to join the values in column B by **"-"** while their values in column A are the same. So, the expected outputs are as below:

**["2-257-258-8-260", "24-26-234", "14-22-78"]**

Can anyone help me how can I get these results.

Thanks in advance