input/code.cpp: In function 'int main()':
input/code.cpp:18:51: error: no matching function for call to 'find(std::__cxx11::list<char>::iterator, std::__cxx11::list<char>::iterator, char&)'
if (std::find(checked.begin(), checked.end(), c) != checked.end()) continue;
^
In file included from /usr/include/c++/7/bits/locale_facets.h:48:0,
from /usr/include/c++/7/bits/basic_ios.h:37,
from /usr/include/c++/7/ios:44,
from /usr/include/c++/7/ostream:38,
from /usr/include/c++/7/iostream:39,
from input/code.cpp:1:
/usr/include/c++/7/bits/streambuf_iterator.h:369:5: note: candidate: template<class _CharT2> typename __gnu_cxx::__enable_if<std::__is_char<_CharT2>::__value, std::istreambuf_iterator<_CharT> >::__type std::find(std::istreambuf_iterator<_CharT>, std::istreambuf_iterator<_CharT>, const _CharT2&)
find(istreambuf_iterator<_CharT> __first,
^...