foo.cc:4:1: error: expected initializer before 'int'
 int fibonacci(int n)
 ^~~
foo.cc: In function 'int main()':
foo.cc:20:6: error: 'n' was not declared in this scope
 cin>>n;
      ^
foo.cc:20:6: note: suggested alternative: 'yn'
 cin>>n;
      ^
      yn
foo.cc:21:8: error: 'f' was not declared in this scope
  int s=f(n);
        ^
foo.cc:22:12: error: 'a1' was not declared in this scope
  cout<<a0<<a1;
            ^~
foo.cc:22:12: note: suggested alternative: 'a0'
  cout<<a0<<a1;
            ^~
            a0
foo.cc:21:6: warning: unused variable 's' [-Wunused-variable]
  int s=f(n);
      ^

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。