foo.cc: In function 'int main()':
foo.cc:19:2: error: 'cin' was not declared in this scope
  cin>>a;
  ^~~
foo.cc:19:2: note: suggested alternative: 'sin'
  cin>>a;
  ^~~
  sin
foo.cc:20:2: error: 'cout' was not declared in this scope
  cout<<floor( ( 1.0*aa(a) )/( aa(a)/2) ); 
  ^~~~
foo.cc:20:2: note: suggested alternative: 'cosl'
  cout<<floor( ( 1.0*aa(a) )/( aa(a)/2) ); 
  ^~~~
  cosl

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