foo.cc:3:17: error: 'std\U0000ff1b' is not a namespace-name
    3 | using namespace std；
      |                 ^~~~~
foo.cc:3:22: error: expected ';' before 'int'
    3 | using namespace std；
      |                      ^
      |                      ;
    4 | int main()
      | ~~~                   
foo.cc: In function 'int main()':
foo.cc:7:5: error: 'cin' was not declared in this scope; did you mean 'std::cin'?
    7 |     cin >> a >> b;
      |     ^~~
      |     std::cin
In file included from stdc++.h:75:
/nix/store/1gf2flfqnpqbr1b4p4qz2f72y42bs56r-gcc-11.3.0/include/c++/11.3.0/iostream:60:18: note: 'std::cin' declared here
   60 |   extern istream cin;           /// Linked to standard input
      |                  ^~~
foo.cc:8:5: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
    8 |     cout << a + b ;
      |     ^~~~
      |     std::cout
In file included from stdc++.h:75:
/nix/store/1gf2flfqnpqbr1b4p4qz2f72y42bs56r-gcc-11.3.0/include/c++/11.3.0/iostream:61:18: note: 'std::cout' declared here
   61 |   extern ostream cout;          /// Linked to standard output
      |                  ^~~~

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