foo.cc:3:7: error: expected nested-name-specifier before 'namesapace'
    3 | using namesapace std;
      |       ^~~~~~~~~~
foo.cc: In function 'int main()':
foo.cc:7:2: error: 'cin' was not declared in this scope; did you mean 'std::cin'?
    7 |  cin>>n;
      |  ^~~
      |  std::cin
In file included from foo.cc:1:
/usr/include/c++/9/iostream:60:18: note: 'std::cin' declared here
   60 |   extern istream cin;  /// Linked to standard input
      |                  ^~~

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