Distinct elements related to another column

Hello,

I have the following table:

| A  | B  |
|----|----|
| A1 | M1 |
| A1 | M2 |
| A2 | M5 |
| A2 | M3 |
| A2 | M1 |
| A2 | M3 |
| A3 | M7 |
| A3 | M1 |

I need to find the distinct elements on the column 'A' and to create another column with the first element of the column 'B' found for the element in 'A'. The result will be something like this:

| A  | B  |
|----|----|
| A1 | M1 |
| A2 | M5 |
| A3 | M7 |

I've already tried several ways but I don't know how to obtain the final result...