foo.cc: In function 'int s(int)':
foo.cc:7:8: warning: unused variable 'c' [-Wunused-variable]
    7 |  int b,c,u=0;
      |        ^
foo.cc:8:9: warning: unused variable 'd' [-Wunused-variable]
    8 |  double d;
      |         ^
foo.cc: In function 'int main()':
foo.cc:21:9: warning: unused variable 'l' [-Wunused-variable]
   21 | int a,i,l;
      |         ^

[Hydro](https://hydro.ac)提供评测服务