foo.cc: In function ‘int rs(int, int, int)’:
foo.cc:23:1: warning: control reaches end of non-void function [-Wreturn-type]
   23 | }
      | ^
foo.cc: In function ‘int yunsuan(int, int, int, int)’:
foo.cc:57:16: warning: ‘ret’ may be used uninitialized [-Wmaybe-uninitialized]
   57 |         return ret;
      |                ^~~
foo.cc:26:13: note: ‘ret’ was declared here
   26 |         int ret,ax,bx;
      |             ^~~