comparison of values in formula attribute

Hello everyone.

I have a question about formula attributes. I would like to compare received attribute values and output only the smallest value. Now I do not know how to achieve this.

With the formula R106:122", ";A5; all sheet numbers (label) are returned. For example "136, 135". Now I want to compare these values and output only the smaller value, i.e. "135". But the system etc. can be mapped to several sheets (three, four, five etc.) and so even more values have to be compared. Is there some kind of loop to compare and output the smallest number?

Thanks in advance for your help