Here is my procedure.it has no errors because it get the limit by subtracting the length of the letters that will be excluded.3 blocks can be reduced by setting the limit to a static number which is 77 ( if you want i can remove them 
).But the app will crash for the large numbers.That doesn’t happen in this procedure.:
But unfortunately,It has 51 blocks 
Also another 3 blocks can be reduced by making the Exclude character input as a list.And not converting it.