# [Perl 6], 38 bytes

<!-- language-all: lang-perl6 -->

    {+(1...all ~*∉$_,*.comb==.max.comb)}

[Try it online!][TIO-jtpanep1]

[Perl 6]: https://github.com/nxadm/rakudo-pkg
[TIO-jtpanep1]: https://tio.run/##K0gtyjH7n1upoJamYKvwv1pbw1BPTy8xJ0ehTutRR6dKvI6WXnJ@bpKtrV5uYgWYqVn7vzixUiFNI1rJ0MBASQdIGirFalpzwUQtgWKWQBlkMSUdBaWS1OISFEGwAFACLPgfAA "Perl 6 – Try It Online"

Anonymous codeblock that takes input as a list of two strings, and returns the first number that is the same length as the string with the maximum length, and is not equal to either string.

### Explanation:

~~~
{                                  }  # Anonymous codeblock
   1...                        # Starting from 1, increment until
       all      ,                # Both:
           ~*∉$_                   # The number is not in the input
                 *.comb            # And the length of the number
                       ==.max.comb # Is equal to the maximum length
 +(                               )  # Return the length of the sequence
~~~