I'm probably asking an stupid question but here it is.
I'm exporting from another systems a list of Part Numbers that comes with
one digit in the end that it is not necessary. The only problem is that I
have PN with 4 and 5 digits. For Example:

Exported PN Correct PN
25780 2578
254780 25478
547881 54788

Is there a formula that will take this last digit of? I cannot use Left or
Right because the length of the PN.

Thanks for your help.

Marcelo