Search for C function from assembly through reverse

Question

I am trying to learn more about x86 build. I have a secret function assembly code. All I know about this function is that it should return an integer and has an integer as an argument:

int mystery(int n){}

Assembly for this function

0000000000400526 <mystery_util>:
  400526:    89 f8                    mov    %edi,%eax
  400528:    d1 e8                    shr    %eax
  40052a:    83 e7 01                 and    $0x1,%edi
  40052d:    01 f8                    add    %edi,%eax
  40052f:    c3                       retq   

0000000000400530 <mystery>:
  400530:    89 f8                    mov    %edi,%eax
  400532:    8d 3c fd 00 00 00 00     lea    0x0(,%rdi,8),%edi
  400539:    29 c7                    sub    %eax,%edi
  40053b:    83 c7 04                 add    $0x4,%edi
  40053e:    e8 e3 ff ff ff           callq  400526 <mystery_util>
  400543:    f3 c3                    repz retq

I don’t understand how to write this as a function of C. If there is callq, does this mean that there are two different functions?

I am trying to write this in a single function that returns an integer. I see how it can return a boolean, but can there be a way to return an integer?