How to automatically remove part of the information in a returned cell

[mss90]

I wish to automatically get my excel sheet to populate my A column with sample IDs copied into a different worksheet within the same excel project. I achieve this by simply adding =TRANSPOSE('Worksheet1'!C6:OS6) into column A in worksheet2 starting at A2. Sometimes the information taken from worksheet1 contains additional information that I wish to strip away. See example below;

Example: In cell A2 I have "P1-1"
What I copied into worksheet1: "P1-1"
What I got in column A in worksheet2: "P1-1"
What I would want to get in column A in worksheet2: "P1"

Is there a formula to automatically strip away "-0" in this case? What comes after the dash may vary so it would be good to just get excel to remove the dash and everything after it.

Please advice.