foo.cc: In function 'int main()':
foo.cc:6:22: warning: unused variable 'f' [-Wunused-variable]
    6 |         double a,b,c,f,d,e;
      |                      ^
foo.cc:6:24: warning: unused variable 'd' [-Wunused-variable]
    6 |         double a,b,c,f,d,e;
      |                        ^
foo.cc:6:26: warning: unused variable 'e' [-Wunused-variable]
    6 |         double a,b,c,f,d,e;
      |                          ^

[Hydro](https://hydro.ac)提供评测服务