/in/foo.c: In function 'isperfectnum':
/in/foo.c:16:5: warning: 'main' is normally a non-static function [-Wmain]
   16 | int main()
      |     ^~~~
/in/foo.c:22:1: error: expected declaration or statement at end of input
   22 | }
      | ^
/in/foo.c:23: warning: control reaches end of non-void function [-Wreturn-type]
/in/foo.c: At top level:
/in/foo.c:16:5: warning: 'main' defined but not used [-Wunused-function]
   16 | int main()
      |     ^~~~