What is the mistake in logic of the following code?

Question

https://code.sololearn.com/c9XPKbJqHcIm/?ref=app

Answer 1

Note: you don't need to put something in your for statement when it doesn't make sense.
for(;a<b;a++)
works just fine for line 7. You could also code:
for(;++x<z;)
if you have a time it makes sense.