/in/foo.c: In function 'main':
/in/foo.c:7:36: error: 'c' undeclared (first use in this function)
    7 |         scanf("%lf,%lf,%lf",&a,&b,&c);
      |                                    ^
/in/foo.c:7:36: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:10:17: error: 'A' undeclared (first use in this function)
   10 |                 A=-b/c;
      |                 ^
/in/foo.c:5:20: warning: unused variable 'c\U0000ff0cA' [-Wunused-variable]
    5 |         double a,b,c，A,B;
      |                    ^~~~