/in/foo.c: In function 'main':
/in/foo.c:7:29: error: 'c' undeclared (first use in this function)
    7 |     scanf("%d,%d,%d",&a,&b,&c);
      |                             ^
/in/foo.c:7:29: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:13:12: error: 'C' undeclared (first use in this function)
   13 |            C=a+b+c;
      |            ^
/in/foo.c:5:13: warning: unused variable 'c\U0000ff0cC' [-Wunused-variable]
    5 |     int a,b,c，C;
      |             ^~~~