Fetching first four character from Parameter

Hi Team,

I'm creating a parameter in Power Query Editor which consists of branch_id_name, For Ex. 1116-madhya pradesh.

This parameter is bound to my branch table with branch_id_name, which we are using as slicer.

But there are different  joins in my query perform joins based on branch_id column which is 1116 first four character from branch_id_name.

Now, can anybody let me know how can I extract first four character from my parameter in advance query editor?

Attached one referencequery in screenshot which we using in advance editor, idea is to fetch first four character from parameter value. 

Thanks in advance!!