foo.c: In function 'bei':
foo.c:38:13: warning: unused variable 'c' [-Wunused-variable]
   38 |         int c=x1*x2/a;
      |             ^
foo.c: In function 'yue':
foo.c:19:1: warning: control reaches end of non-void function [-Wreturn-type]
   19 | }
      | ^
foo.c: In function 'bei':
foo.c:40:1: warning: control reaches end of non-void function [-Wreturn-type]
   40 | }
      | ^

[Hydro](https://hydro.ac)提供评测服务