foo.cc: In function 'int sb(int)':
foo.cc:7:12: warning: unused variable 'd' [-Wunused-variable]
    7 |  int i,s=0,d;
      |            ^
foo.cc: In function 'int main()':
foo.cc:27:7: error: 'd' was not declared in this scope
   27 |       d++;
      |       ^
foo.cc:30:8: error: 'd' was not declared in this scope
   30 |  cout<<d;
      |        ^

[Hydro](https://hydro.ac)提供评测服务