/in/foo.c: In function 'main':
/in/foo.c:13:8: warning: implicit declaration of function 'abs' [-Wimplicit-function-declaration]
   ans+=abs(a[i]-a[mid]);
        ^~~
/in/foo.c: In function 'Sort':
/in/foo.c:27:5: error: 'q' undeclared (first use in this function)
   *(q+1) = tmp; 
     ^
/in/foo.c:27:5: note: each undeclared identifier is reported only once for each function it appears in