/in/foo.cc:2:7: error: expected nested-name-specifier before 'namepsace'
 using namepsace std;
       ^~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:6:2: error: 'cin' was not declared in this scope
  cin>>a>>b;
  ^~~
/in/foo.cc:6:2: note: suggested alternative:
In file included from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:75:0,
                 from /in/foo.cc:1:
/usr/include/c++/6/iostream:60:18: note:   'std::cin'
   extern istream cin;  /// Linked to standard input
                  ^~~
/in/foo.cc:7:2: error: 'cout' was not declared in this scope
  cout<<"C="<<fixed<<setprecision(2)a+b<<" ";
  ^~~~
/in/foo.cc:7:2: note: suggested alternative:
In file included from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:75:0,
                 from /in/foo.cc:1:
/usr/include/c++/6/iostream:61:18: note:   'std::cout'
   extern ostream cout;  /// Linked to standard output
                  ^~~~
/in/foo.cc:7:14: error: 'fixed' was not declared in this scope
  cout<<"C="<<fixed<<setprecision(2)a+b<<" ";
              ^~~~~
/in/foo.cc:7:14: note: suggested alternative:
In file included from /usr/include/c++/6/ios:42:0,
                 from /usr/include/c++/6/istream:38,
                 from /usr/include/c++/6/sstream:38,
                 from /usr/include/c++/6/complex:45,
                 from /usr/include/c++/6/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:52,
                 from /in/foo.cc:1:
/usr/include/c++/6/bits/ios_base.h:1041:3: note:   'std::fixed'
   fixed(ios_base& __base)
   ^~~~~
/in/foo.cc:7:35: error: 'setprecision' was not declared in this scope
  cout<<"C="<<fixed<<setprecision(2)a+b<<" ";
                                   ^
/in/foo.cc:7:35: note: suggested alternative:
In file included from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:72:0,
                 from /in/foo.cc:1:
/usr/include/c++/6/iomanip:195:3: note:   'std::setprecision'
   setprecision(int __n)
   ^~~~~~~~~~~~