foo.cc:2:7: error: expected nested-name-specifier before 'naemspace'
 using naemspace std;
       ^~~~~~~~~
foo.cc: In function 'int main()':
foo.cc:6:2: error: 'cin' was not declared in this scope
  cin>>n;
  ^~~
foo.cc:6:2: note: suggested alternative:
In file included from foo.cc:1:0:
/usr/include/c++/7/iostream:60:18: note:   'std::cin'
   extern istream cin;  /// Linked to standard input
                  ^~~
foo.cc:8:2: error: 'cout' was not declared in this scope
  cout<<321<<"-"<<123<<"="<<198<<endl;
  ^~~~
foo.cc:8:2: note: suggested alternative:
In file included from foo.cc:1:0:
/usr/include/c++/7/iostream:61:18: note:   'std::cout'
   extern ostream cout;  /// Linked to standard output
                  ^~~~
foo.cc:8:33: error: 'endl' was not declared in this scope
  cout<<321<<"-"<<123<<"="<<198<<endl;
                                 ^~~~
foo.cc:8:33: note: suggested alternative:
In file included from /usr/include/c++/7/iostream:39:0,
                 from foo.cc:1:
/usr/include/c++/7/ostream:590:5: note:   'std::endl'
     endl(basic_ostream<_CharT, _Traits>& __os)
     ^~~~
foo.cc:9:5: error: 'cout' was not declared in this scope
     cout<<981<<"-"<<189<<"="<<792<<endl;
     ^~~~
foo.cc:9:5: note: suggested alternative:
In file included from foo.cc:1:0:
/usr/include/c++/7/iostream:61:18: note:   'std::cout'
   extern ostream cout;  /// Linked to standard output
                  ^~~~
foo.cc:9:36: error: 'endl' was not declared in this scope
     cout<<981<<"-"<<189<<"="<<792<<endl;
                                    ^~~~
foo.cc:9:36: note: suggested alternative:
In file included from /usr/include/c++/7/iostream:39:0,
                 from foo.cc:1:
/usr/include/c++/7/ostream:590:5: note:   'std::endl'
     endl(basic_ostream<_CharT, _Traits>& __os)
     ^~~~