answer.code: In function ‘void solve()’:
answer.code:90:19: error: no matching function for call to ‘std::set<int>::insert(std::string&)’
   90 |         len.insert(s[i]);
      |         ~~~~~~~~~~^~~~~~
In file included from /usr/include/c++/11/set:61,
                 from answer.code:2:
/usr/include/c++/11/bits/stl_set.h:566:9: note: candidate: ‘template<class _InputIterator> void std::set<_Key, _Compare, _Alloc>::insert(_InputIterator, _InputIterator) [with _InputIterator = _InputIterator; _Key = int; _Compare = std::less<int>; _Alloc = std::allocator<int>]’
  566 |         insert(_InputIterator __first, _InputIterator __last)
      |         ^~~~~~
/usr/include/c++/11/bits/stl_set.h:566:9: note:   template argument deduction/substitution failed:
answer.code:90:19: note:   candidate expects 2 arguments, 1 provided
   90 |         len.insert(s[i]);
      |         ~~~~~~~~~~^~~~~~
In file included from /usr/include/c++/11/set:61,
                 from answer.code:2:
/usr/include/c++/11/bits/stl_set.h:509:7: note: candidate: ‘std::pair<typename std::_Rb_tree<_Key, _Key, std::_Identity<_Tp>, _Compare, typename __gnu_cxx::__alloc_traits<_Alloc>::rebind<_Key>::other>::const_iterator, bool> std::set<_Key, _Compare, _Alloc>::insert(const value_type&) [with _Key = int; _Compare = std::less<int>; _Alloc = std::allocator<int>; typename std::_Rb_tree<_Key, _Key, std::_Identity<_Tp>, _Compare, typename __gnu_cxx::__alloc_traits<_Alloc>::rebind<_Key>::other>::const_iterator = std::_Rb_tree<int, int, std::_Identity<int>, std::less<int>, std::allocator<int> >::const_iterator; typename __gnu_cxx::__alloc_traits<_Alloc>::rebind<_Key>::other = std::allocator<int>; typename __gnu_cxx::__alloc_traits<_Alloc>::rebind<_Key> = __gnu_cxx::__alloc_traits<std::allocator<int>, int>::rebind<int>; typename _Alloc::value_type = int; std::set<_Key, _Compare, _Alloc>::value_type = int]’
  509 |       insert(const value_type& __x)
      |       ^~~~~~
/usr/include/c++/11/bits/stl_set.h:509:32: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const value_type&’ {aka ‘const int&’}
  509 |       insert(const value_type& __x)
      |              ~~~~~~~~~~~~~~~~~~^~~
/usr/include/c++/11/bits/stl_set.h:518:7: note: candidate: ‘std::pair<typename std::_Rb_tree<_Key, _Key, std::_Identity<_Tp>, _Compare, typename __gnu_cxx::__alloc_traits<_Alloc>::rebind<_Key>::other>::const_iterator, bool> std::set<_Key, _Compare, _Alloc>::insert(std::set<_Key, _Compare, _Alloc>::value_type&&) [with _Key = int; _Compare = std::less<int>; _Alloc = std::allocator<int>; typename std::_Rb_tree<_Key, _Key, std::_Identity<_Tp>, _Compare, typename __gnu_cxx::__alloc_traits<_Alloc>::rebind<_Key>::other>::const_iterator = std::_Rb_tree<int, int, std::_Identity<int>, std::less<int>, std::allocator<int> >::const_iterator; typename __gnu_cxx::__alloc_traits<_Alloc>::rebind<_Key>::other = std::allocator<int>; typename __gnu_cxx::__alloc_traits<_Alloc>::rebind<_Key> = __gnu_cxx::__alloc_traits<std::allocator<int>, int>::rebind<int>; typename _Alloc::value_type = int; std::set<_Key, _Compare, _Alloc>::value_type = int]’
  518 |       insert(value_type&& __x)
      |       ^~~~~~
/usr/include/c++/11/bits/stl_set.h:518:27: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘std::set<int>::value_type&&’ {aka ‘int&&’}
  518 |       insert(value_type&& __x)
      |              ~~~~~~~~~~~~~^~~
/usr/include/c++/11/bits/stl_set.h:546:7: note: candidate: ‘std::set<_Key, _Compare, _Alloc>::iterator std::set<_Key, _Compare, _Alloc>::insert(std::set<_Key, _Compare, _Alloc>::const_iterator, const value_type&) [with _Key = int; _Compare = std::less<int>; _Alloc = std::allocator<int>; std::set<_Key, _Compare, _Alloc>::iterator = std::_Rb_tree<int, int, std::_Identity<int>, std::less<int>, std::allocator<int> >::const_iterator; std::set<_Key, _Compare, _Alloc>::const_iterator = std::_Rb_tree<int, int, std::_Identity<int>, std::less<int>, std::allocator<int> >::const_iterator; std::set<_Key, _Compare, _Alloc>::value_type = int]’
  546 |       insert(const_iterator __position, const value_type& __x)
      |       ^~~~~~
/usr/include/c++/11/bits/stl_set.h:546:7: note:   candidate expects 2 arguments, 1 provided
/usr/include/c++/11/bits/stl_set.h:551:7: note: candidate: ‘std::set<_Key, _Compare, _Alloc>::iterator std::set<_Key, _Compare, _Alloc>::insert(std::set<_Key, _Compare, _Alloc>::const_iterator, std::set<_Key, _Compare, _Alloc>::value_type&&) [with _Key = int; _Compare = std::less<int>; _Alloc = std::allocator<int>; std::set<_Key, _Compare, _Alloc>::iterator = std::_Rb_tree<int, int, std::_Identity<int>, std::less<int>, std::allocator<int> >::const_iterator; std::set<_Key, _Compare, _Alloc>::const_iterator = std::_Rb_tree<int, int, std::_Identity<int>, std::less<int>, std::allocator<int> >::const_iterator; std::set<_Key, _Compare, _Alloc>::value_type = int]’
  551 |      ...