Is it possible to combine addition into one formula, and if more than 9, then add these numbers?

Question

excel

https://docs.google.com/spreadsheets/d/1bKzv84kFGu...

I want to combine two formulas. otherwise you will have to write a lot of formulas. The task is to add two numbers
in cell K4 ? and if the sum is greater than 9, i.e. a two-digit number, for example 13, then add 1 + 3 and you need to see the value 4 in the cell.

I do this, I don’t get the desired result:
=IF(($N$1+$G$1)<10;K4;(PSTR(K4;1 ;1)+MID(K4;2;1)))

Tell me, please, what needs to be corrected in the formula?

Answer 1

=IF($N$1+$G$1>9;1+3)
upd

==IF(($N$1+$G$1)<10;$N$1+$G$1;(MID($N$1+$G$1;1;1)+MID($N$1+$G$1;2;1)))