foo.cc: In function 'int main()':
foo.cc:10:2: error: 'cin' was not declared in this scope
  cin>>a>>b>>c;//>>g;
  ^~~
foo.cc:10:2: note: suggested alternative: 'main'
  cin>>a>>b>>c;//>>g;
  ^~~
  main
foo.cc:29:2: error: 'cout' was not declared in this scope
  cout<<a<<"-"<<k<<"-"<<g;
  ^~~~
foo.cc: In function 'long long int ad(long long int, long long int)':
foo.cc:101:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^

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