/in/foo.cc: In function 'int main()':
/in/foo.cc:11:15: error: 'endl' was not declared in this scope
 std::cout<<b<<endl;
               ^~~~
/in/foo.cc:11:15: 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)
     ^~~~