foo.cc: In function 'int main()':
foo.cc:7:9: error: 'cin' was not declared in this scope; did you mean 'std::cin'?
    7 |         cin>>a>>k;
      |         ^~~
      |         std::cin
In file included from stdc++.h:75:
/nix/store/1x1q5sqa0ilbi8fz7aayk02pjy5g7jhh-gcc-12.3.0/include/c++/12.3.0/iostream:60:18: note: 'std::cin' declared here
   60 |   extern istream cin;           /// Linked to standard input
      |                  ^~~
foo.cc:8:9: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
    8 |         cout << std::fixed << setprecision(k) << a << endl;
      |         ^~~~
      |         std::cout
/nix/store/1x1q5sqa0ilbi8fz7aayk02pjy5g7jhh-gcc-12.3.0/include/c++/12.3.0/iostream:61:18: note: 'std::cout' declared here
   61 |   extern ostream cout;          /// Linked to standard output
      |                  ^~~~
foo.cc:8:31: error: 'setprecision' was not declared in this scope; did you mean 'std::setprecision'?
    8 |         cout << std::fixed << setprecision(k) << a << endl;
      |                               ^~~~~~~~~~~~
      |                               std::setprecision
In file included from stdc++.h:72:
/nix/store/1x1q5sqa0ilbi8fz7aayk02pjy5g7jhh-gcc-12.3.0/include/c++/12.3.0/iomanip:195:3: note: 'std::setprecision' declared here
  195 |   setprecision(int __n)
      |   ^~~~~~~~~~~~
foo.cc:8:55: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
    8 |         cout << std::fixed << setprecision(k) << a << endl;
      |                                                       ^~~~
      |                                                       std::endl
In file included from /nix/store/1x1q5sqa0ilbi8fz7aayk02pjy5g7jhh-gcc-12.3.0/include/c++/12.3.0/istream:39,
                 from /nix/store/1x1q5sqa0ilbi8fz7aayk02pjy5g7jhh-gcc-12.3.0/include/c++/12.3.0/sstream:38,
                 from /nix/store/1x1q5sqa0ilbi8fz7aayk02pjy5g7jhh-gcc-12.3.0/include/c++/12.3.0/complex:45,
                 from /nix/store/1x1q5sqa0ilbi8fz7aayk02pjy5g7jhh-gcc-12.3.0/include/c++/12.3.0/ccomplex:39,
                 from stdc++.h:54:
/nix/store/1x1q5sqa0ilbi8fz7aayk02pjy5g7jhh-gcc-12.3.0/include/c++/12.3.0/ostream:688:5: note: 'std::endl' declared here
  688 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~

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