/in/foo.cc: In function 'int main()':
/in/foo.cc:6:5: error: 'cin' was not declared in this scope
     cin>>l>>v;
     ^~~
/in/foo.cc:6:5: note: suggested alternative:
In file included from /in/foo.cc:1:0:
/usr/include/c++/6/iostream:60:18: note:   'std::cin'
   extern istream cin;  /// Linked to standard input
                  ^~~
/in/foo.cc:7:5: error: 'cout' was not declared in this scope
     cout<<fixed<<setprecision(1)<<l*2/3<<endl<<l*2/3/v<<endl;
     ^~~~
/in/foo.cc:7:5: note: suggested alternative:
In file included from /in/foo.cc:1:0:
/usr/include/c++/6/iostream:61:18: note:   'std::cout'
   extern ostream cout;  /// Linked to standard output
                  ^~~~
/in/foo.cc:7:11: error: 'fixed' was not declared in this scope
     cout<<fixed<<setprecision(1)<<l*2/3<<endl<<l*2/3/v<<endl;
           ^~~~~
/in/foo.cc:7:11: note: suggested alternative:
In file included from /usr/include/c++/6/ios:42:0,
                 from /usr/include/c++/6/ostream:38,
                 from /usr/include/c++/6/iostream:39,
                 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:7:32: error: 'setprecision' was not declared in this scope
     cout<<fixed<<setprecision(1)<<l*2/3<<endl<<l*2/3/v<<endl;
                                ^
/in/foo.cc:7:32: note: suggested alternative:
In file included from /in/foo.cc:2:0:
/usr/include/c++/6/iomanip:195:3: note:   'std::setprecision'
   setprecision(int __n)
   ^~~~~~~~~~~~
/in/foo.cc:7:42: error: 'endl' was not declared in this scope
     cout<<fixed<<setprecision(1)<<l*2/3<<endl<<l*2/3/v<<endl;
                                          ^~~~
/in/foo.cc:7:42: note: suggested alternative:
In file included from /usr/include/c++/6/iostream:39:0,
                 from /in/foo.cc:1:
/usr/include/c++/6/ostream:590:5: note:   'std::endl'
     endl(basic_ostream<_CharT, _Traits>& __os)
     ^~~~