/in/foo.c: In function 'main':
/in/foo.c:29:11: warning: unused variable 'd' [-Wunused-variable]
 int a,b,c,d;
           ^
/in/foo.c:29:9: warning: unused variable 'c' [-Wunused-variable]
 int a,b,c,d;
         ^
/in/foo.c: In function 'fenshu':
/in/foo.c:25:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^