foo.cc: In function 'int main()':
foo.cc:5:8: warning: unused variable 'b' [-Wunused-variable]
    5 |  int a,b,c;
      |        ^
foo.cc:5:10: warning: unused variable 'c' [-Wunused-variable]
    5 |  int a,b,c;
      |          ^

[Hydro](https://hydro.ac)提供评测服务