I need to take one column as Key and other as values, and get resulting sheet with one ke

Question,
Column A has key values. IncolumnB, few rows just have one values and few have multiple values. I.e.
A B
1 x
2 x,y,z
3 y,z,e
4 n,m
I need the resulting sheet as follows,
A B
1 x
2 x
2 y
2 z
3 y
3 z
3 e
4 n
4 m


I have a huge list for this,
If anyone can help.

THanks, I have figured the issue.
But thank you very much for the time.
cheers!