/in/foo.cc: In function 'int main()':
/in/foo.cc:7:5: error: 'cin' was not declared in this scope
     cin>>T;
     ^~~
/in/foo.cc:8:5: error: 'string' was not declared in this scope
     string a;//这里强调要用string类！！！题目说了a的数值达到了10的1000次方（1后面1000个0，啧啧）
     ^~~~~~
/in/foo.cc:11:11: error: 'a' was not declared in this scope
      cin>>a;
           ^
/in/foo.cc:12:6: error: 'cout' was not declared in this scope
      cout<<a<<endl;
      ^~~~
/in/foo.cc:12:15: error: 'endl' was not declared in this scope
      cout<<a<<endl;
               ^~~~