/in/foo.cc: In function 'int main()':
/in/foo.cc:7:6: error: storage size of 'a' isn't known
  int a[][2];
      ^
/in/foo.cc:8:2: error: 'cin' was not declared in this scope
  cin>>n;
  ^~~
/in/foo.cc:8:2: note: suggested alternative: 'main'
  cin>>n;
  ^~~
  main
/in/foo.cc:24:5: error: 'cout' was not declared in this scope
     cout<<num<<endl;
     ^~~~
/in/foo.cc:24:16: error: 'endl' was not declared in this scope
     cout<<num<<endl;
                ^~~~
/in/foo.cc:24:16: note: suggested alternative: 'enum'
     cout<<num<<endl;
                ^~~~
                enum