/in/foo.cc: In function 'int rs(int, int, int)':
/in/foo.cc:25:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^
/in/foo.cc: In function 'int yunsuan(int, int, int, int)':
/in/foo.cc:59:9: warning: 'ret' may be used uninitialized in this function [-Wmaybe-uninitialized]
  return ret;
         ^~~