/in/foo.cc:3:11: error: 'double y1' redeclared as different kind of entity
    3 | double x1,y1,x2,y2,dis;
      |           ^~
In file included from /usr/include/features.h:489,
                 from /usr/include/x86_64-linux-gnu/c++/12/bits/os_defines.h:39,
                 from /usr/include/x86_64-linux-gnu/c++/12/bits/c++config.h:655,
                 from /usr/include/c++/12/cassert:43,
                 from /usr/include/x86_64-linux-gnu/c++/12/bits/stdc++.h:33,
                 from /in/foo.cc:1:
/usr/include/x86_64-linux-gnu/bits/mathcalls.h:224:1: note: previous declaration 'double y1(double)'
  224 | __MATHCALL (y1,, (_Mdouble_));
      | ^~~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:6:16: error: no match for 'operator>>' (operand types are 'std::basic_istream<char>::__istream_type' {aka 'std::basic_istream<char>'} and 'double(double) noexcept' {aka 'double(double)'})
    6 |         cin>>x1>>y1>>x2>>y2;
      |         ~~~~~~~^~~~
      |            |     |
      |            |     double(double) noexcept {aka double(double)}
      |            std::basic_istream<char>::__istream_type {aka std::basic_istream<char>}
In file included from /usr/include/c++/12/sstream:38,
                 from /usr/include/c++/12/complex:45,
                 from /usr/include/c++/12/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/12/bits/stdc++.h:54:
/usr/include/c++/12/istream:120:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(__istream_type& (*)(__istream_type&)) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  120 |       operator>>(__istream_type& (*__pf)(__istream_type&))
      |       ^~~~~~~~
/usr/include/c++/12/istream:120:7: note:   conversion of argument 1 would be ill-formed:
/in/foo.cc:6:18: error: invalid conversion from 'double (*)(double) noexcept' {aka 'double (*)(double)'} to 'std::basic_istream<char>::__istream_type& (*)(std::basic_istream<char>::__istream_type&)' {aka 'std::basic_istream<char>& (*)(std::basic_istream<char>&)'} [-fpermissive]
    6 |         cin>>x1>>y1>>x2>>y2;
      |                  ^~
      |                  |
      |                  double (*)(double) noexcept {aka double (*)(double)}
/usr/include/c++/12/istream:124:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(__ios_type& (*)(__ios_type&)) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>; __ios_type = std::basic_ios<char>]' (near match)
  124 |       operator>>(__ios_type& (*__pf)(__ios_type&))
      |       ^~~~~~~~
/usr/include/c++/12/istream:124:7: note:   conversion of argument 1 would be ill-formed:
/in/foo.cc:6:18: error: invalid conversion from 'double (*)(double) noexcept' {aka 'double (*)(double)'} to 'std::basic_istream<char>::__ios_type& (*)(std::basic_istream<char>::__ios_type&)' {aka 'std::basic_ios<char>& (*)(std::basic_ios<char>&)'} [-fpermissive]
    6 |         cin>>x1>>y1>>x2>>y2;
      |                  ^~
      |                  |
      |                  double (*)(double) noexcept {aka double (*)(double)}
/usr/include/c++/12/istream:131:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(std::ios_base& (*)(std::ios_base&)) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  131 |       operator>>(ios_base& (*__pf)(ios_base&))
      |       ^~~~~~~~
/usr/include/c++/12/istream:131:7: note:   conversion of argument 1 would be ill-formed:
/in/foo.cc:6:18: error: invalid conversion from 'double (*)(double) noexcept' {aka 'double (*)(double)'} to 'std::ios_base& (*)(std::ios_base&)' [-fpermissive]
    6 |         cin>>x1>>y1>>x2>>y2;
      |                  ^~
      |                  |
      |                  double (*)(double) noexcept {aka double (*)(double)}
/usr/include/c++/12/istream:168:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(bool&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  168 |       operator>>(bool& __n)
      |       ^~~~~~~~
/usr/include/c++/12/istream:168:7: note:   conversion of argument 1 would be ill-formed:
/in/foo.cc:6:18: warning: the address of 'double y1(double)' will never be NULL [-Waddress]
    6 |         cin>>x1>>y1>>x2>>y2;
      |                  ^~
/usr/include/x86_64-linux-gnu/bits/mathcalls.h:224:1: note: 'double y1(double)' declared here
  224 | __MATHCALL (y1,, (_Mdouble_));
      | ^~~~~~~~~~
/in/foo.cc:6:18: error: cannot bind non-const lvalue reference of type 'bool&' to a value of type 'double (*)(double) noexcept' {aka 'double (*)(double)'}
    6 |         cin>>x1>>y1>>x2>>y2;
      |                  ^~
/usr/include/c++/12/istream:172:7: note: candidate: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(short int&) [with _CharT = char; _Traits = std::char_traits<char>]' (near match)
  172 |       operator>>(short& __n);
      |       ^~~~~~~~
/usr/include/c++/12/istream:172:7: note:   conversion of argument 1 would be ill-formed:
/in/foo.cc:6:18: error: invalid conversion from 'double (*)(double) noexcept' {aka 'double (*)(double)'} to 'short int' [-fpermissive]
    6 |         cin>>x1>>y1>>x2>>y2;
      |                  ^~
      |                  |
      |                  double (*)(double) noexcept {aka double (*)(double)}
/in/foo.cc:6:18: error: cannot bind rvalue '(short int)y1' to 'short int&'
/usr/include/c++/12/istream:175:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(short unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  175 |       operator>>(unsigned short& __n)
      |       ^~~~~~~~
/usr/include/c++/12/istream:175:7: note:   conversion of argument 1 would be ill-formed:
/in/foo.cc:6:18: error: invalid conversion from 'double (*)(double) noexcept' {aka 'double (*)(double)'} to 'short unsigned int' [-fpermissive]
    6 |         cin>>x1>>y1>>x2>>y2;
      |                  ^~
      |                  |
      |                  double (*)(double) noexcept {aka double (*)(double)}
/in/foo.cc:6:18: error: cannot bind rvalue '(short unsigned int)y1' to 'short unsigned int&'
/usr/include/c++/12/istream:179:7: note: candidate: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(int&) [with _CharT = char; _Traits = std::char_traits<char>]' (near match)
  179 |       operator>>(int& __n);
      |       ^~~~~~~~
/usr/include/c++/12/istream:179:7: note:   conversion of argument 1 would be ill-formed:
/in/foo.cc:6:18: error: invalid conversion from 'double (*)(double) noexcept' {aka 'double (*)(double)'} to 'int' [-fpermissive]
    6 |         cin>>x1>>y1>>x2>>y2;
      |                  ^~
      |                  |
      |                  double (*)(double) noexcept {aka double (*)(double)}
/in/foo.cc:6:18: error: cannot bind rvalue '(int)y1' to 'int&'
/usr/include/c++/12/istream:182:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  182 |       operator>>(unsigned int& __n)
      |       ^~~~~~~~
/usr/include/c++/12/istream:182:7: note:   conversion of argument 1 would be ill-formed:
/in/foo.cc:6:18: error: invalid conversion from 'double (*)(double) noexcept' {aka 'double (*)(double)'} to 'unsigned int' [-fpermissive]
    6 |         cin>>x1>>y1>>x2>>y2;
      |                  ^~
      |                  |
      |                  double (*)(double) noexcept {aka double (*)(double)}
/in/foo.cc:6:18: error: cannot bind rvalue '(unsigned int)y1' to 'unsigned int&'
/usr/include/c++/12/istream:1