/in/foo.cc: In function 'int main()':
/in/foo.cc:7:5: error: 'cin' was not declared in this scope
     cin >> n;
     ^~~
/in/foo.cc:7:5: note: suggested alternative:
In file included from /in/foo.cc:1:0:
/usr/include/c++/6/iostream:60:18: note:   'std::cin'
   extern istream cin;  /// Linked to standard input
                  ^~~
/in/foo.cc:10:9: error: 'cerr' was not declared in this scope
         cerr << "输入错误，请输入一个整数！" << endl;
         ^~~~
/in/foo.cc:10:9: note: suggested alternative:
In file included from /in/foo.cc:1:0:
/usr/include/c++/6/iostream:62:18: note:   'std::cerr'
   extern ostream cerr;  /// Linked to standard error (unbuffered)
                  ^~~~
/in/foo.cc:10:62: error: 'endl' was not declared in this scope
         cerr << "输入错误，请输入一个整数！" << endl;
                                                              ^~~~
/in/foo.cc:10:62: note: suggested alternative:
In file included from /usr/include/c++/6/iostream:39:0,
                 from /in/foo.cc:1:
/usr/include/c++/6/ostream:590:5: note:   'std::endl'
     endl(basic_ostream<_CharT, _Traits>& __os)
     ^~~~
/in/foo.cc:18:13: error: 'cout' was not declared in this scope
             cout << " " << setw(4) << x;
             ^~~~
/in/foo.cc:18:13: note: suggested alternative:
In file included from /in/foo.cc:1:0:
/usr/include/c++/6/iostream:61:18: note:   'std::cout'
   extern ostream cout;  /// Linked to standard output
                  ^~~~
/in/foo.cc:18:34: error: 'setw' was not declared in this scope
             cout << " " << setw(4) << x;
                                  ^
/in/foo.cc:18:34: note: suggested alternative:
In file included from /in/foo.cc:2:0:
/usr/include/c++/6/iomanip:225:3: note:   'std::setw'
   setw(int __n)
   ^~~~
/in/foo.cc:21:9: error: 'cout' was not declared in this scope
         cout << endl;
         ^~~~
/in/foo.cc:21:9: note: suggested alternative:
In file included from /in/foo.cc:1:0:
/usr/include/c++/6/iostream:61:18: note:   'std::cout'
   extern ostream cout;  /// Linked to standard output
                  ^~~~
/in/foo.cc:21:17: error: 'endl' was not declared in this scope
         cout << endl;
                 ^~~~
/in/foo.cc:21:17: note: suggested alternative:
In file included from /usr/include/c++/6/iostream:39:0,
                 from /in/foo.cc:1:
/usr/include/c++/6/ostream:590:5: note:   'std::endl'
     endl(basic_ostream<_CharT, _Traits>& __os)
     ^~~~