foo.cc: In function 'int main()':
foo.cc:14:6: warning: unused variable 'a' [-Wunused-variable]
  int a,b,c,y=0;
      ^
foo.cc:14:8: warning: unused variable 'b' [-Wunused-variable]
  int a,b,c,y=0;
        ^
foo.cc:14:10: warning: unused variable 'c' [-Wunused-variable]
  int a,b,c,y=0;
          ^

[Hydro](https://hydro.ac)提供评测服务