/in/foo.cc:2:7: error: expected nested-name-specifier before 'namesapce'
    2 | using namesapce std;
      |       ^~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:6:2: error: 'cin' was not declared in this scope; did you mean 'std::cin'?
    6 |  cin>>a>>b;
      |  ^~~
      |  std::cin
In file included from /in/foo.cc:1:
/usr/include/c++/9/iostream:60:18: note: 'std::cin' declared here
   60 |   extern istream cin;  /// Linked to standard input
      |                  ^~~
/in/foo.cc:8:2: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
    8 |  cout<<sum<<endl;
      |  ^~~~
      |  std::cout
In file included from /in/foo.cc:1:
/usr/include/c++/9/iostream:61:18: note: 'std::cout' declared here
   61 |   extern ostream cout;  /// Linked to standard output
      |                  ^~~~
/in/foo.cc:8:13: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
    8 |  cout<<sum<<endl;
      |             ^~~~
      |             std::endl
In file included from /usr/include/c++/9/iostream:39,
                 from /in/foo.cc:1:
/usr/include/c++/9/ostream:599:5: note: 'std::endl' declared here
  599 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~