select only upto second '-' only

Question

I Have table like this......


House_no

6-1
6-1-2
6-1/2
6-1/78
6-12/5
6-3-124 ,hyderabad
6-3/2
6-3-19876 ,yuyu

select only first '-' only.............

I WANT OUTPUT LIKE THIS...........

6-1
6-1/2
6-1/78
6-3/2
6-12/5