answer.code: In function ‘int main()’:
answer.code:56:48: error: no match for ‘operator!=’ (operand types are ‘std::__cxx11::basic_string<char>’ and ‘std::__cxx11::basic_string<char>::size_type’ {aka ‘long unsigned int’})
   56 |             if(i!=x.length()-1 && x.substr(i+1)!='0'*(x.length()-i-1)){
      |                                   ~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
      |                                           |         |
      |                                           |         std::__cxx11::basic_string<char>::size_type {aka long unsigned int}
      |                                           std::__cxx11::basic_string<char>
In file included from /usr/include/c++/11/regex:63,
                 from /usr/include/x86_64-linux-gnu/c++/11/bits/stdc++.h:110,
                 from answer.code:1:
/usr/include/c++/11/bits/regex.h:1208:5: note: candidate: ‘template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::__cxx11::operator==(const std::__cxx11::sub_match<_BiIter>&, std::__cxx11::__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&)’ (reversed)
 1208 |     operator==(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/11/bits/regex.h:1208:5: note:   template argument deduction/substitution failed:
answer.code:56:69: note:   mismatched types ‘const std::__cxx11::sub_match<_BiIter>’ and ‘std::__cxx11::basic_string<char>::size_type’ {aka ‘long unsigned int’}
   56 |             if(i!=x.length()-1 && x.substr(i+1)!='0'*(x.length()-i-1)){
      |                                                                     ^
In file included from /usr/include/c++/11/regex:63,
                 from /usr/include/x86_64-linux-gnu/c++/11/bits/stdc++.h:110,
                 from answer.code:1:
/usr/include/c++/11/bits/regex.h:1375:5: note: candidate: ‘template<class _Bi_iter> bool std::__cxx11::operator==(const std::__cxx11::sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type*)’ (reversed)
 1375 |     operator==(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/11/bits/regex.h:1375:5: note:   template argument deduction/substitution failed:
answer.code:56:69: note:   mismatched types ‘const std::__cxx11::sub_match<_BiIter>’ and ‘std::__cxx11::basic_string<char>::size_type’ {aka ‘long unsigned int’}
   56 |             if(i!=x.length()-1 && x.substr(i+1)!='0'*(x.length()-i-1)){
      |                                                                     ^
In file included from /usr/include/c++/11/regex:63,
                 from /usr/include/x86_64-linux-gnu/c++/11/bits/stdc++.h:110,
                 from answer.code:1:
/usr/include/c++/11/bits/regex.h:1547:5: note: candidate: ‘template<class _Bi_iter> bool std::__cxx11::operator==(const std::__cxx11::sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type&)’ (reversed)
 1547 |     operator==(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/11/bits/regex.h:1547:5: note:   template argument deduction/substitution failed:
answer.code:56:69: note:   mismatched types ‘const std::__cxx11::sub_match<_BiIter>’ and ‘std::__cxx11::basic_string<char>::size_type’ {aka ‘long unsigned int’}
   56 |             if(i!=x.length()-1 && x.substr(i+1)!='0'*(x.length()-i-1)){
      |                                                                     ^
In file included from /usr/include/c++/11/bits/stl_algobase.h:67,
                 from /usr/include/c++/11/bits/specfun.h:45,
                 from /usr/include/c++/11/cmath:1927,
                 from /usr/include/x86_64-linux-gnu/c++/11/bits/stdc++.h:41,
                 from answer.code:1:
/usr/include/c++/11/bits/stl_iterator.h:491:5: note: candidate: ‘template<class _IteratorL, class _IteratorR> constexpr bool std::operator==(const std::reverse_iterator<_IteratorL>&, const std::reverse_iterator<_IteratorR>&) requires requires{{std::operator==::__x->base() == std::operator==::__y->base()} -> decltype(auto) [requires std::convertible_to<<placeholder>, bool>];}’ (reversed)
  491 |     operator==(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/11/bits/stl_iterator.h:491:5: note:   template argument deduction/substitution failed:
answer.code:56:69: note:   mismatched types ‘const std::reverse_iterator<_IteratorL>’ and ‘std::__cxx11::basic_string<char>::size_type’ {aka ‘long unsigned int’}
   56 |             if(i!=x.length()-1 && x.substr(i+1)!='0'*(x.length()-i-1)){
      |                                                                     ^
In file included from /usr/include/c++/11/bits/stl_algobase.h:67,
                 from /usr/include/c++/11/bits/specfun.h:45,
                 from /usr/include/c++/11/cmath:1927,
                 from /usr/include/x86_64-linux-gnu/c++/11/bits/stdc++.h:41,
                 from answer.code:1:
/usr/include/c++/11/bits/stl_iterator.h:1533:5: note: candidate: ‘template<class _IteratorL, class _IteratorR> constexpr bool std::operator==(const std::m...