/in/foo.cc: In function 'int main()':
/in/foo.cc:27:16: warning: format '%s' expects argument of type 'char*', but argument 2 has type 'std::__cxx11::string (*)[2] {aka std::__cxx11::basic_string<char> (*)[2]}' [-Wformat=]
   scanf("%s",&a);
                ^
/in/foo.cc:28:10: error: no match for 'operator==' (operand types are 'std::__cxx11::string {aka std::__cxx11::basic_string<char>}' and 'char')
   if(a[0]=='A'){
      ~~~~^~~~~
In file included from /usr/include/c++/6/regex:62:0,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:110,
                 from /in/foo.cc:1:
/usr/include/c++/6/bits/regex.h:940:5: note: candidate: template<class _BiIter> bool std::__cxx11::operator==(const std::__cxx11::sub_match<_BiIter>&, const std::__cxx11::sub_match<_BiIter>&)
     operator==(const sub_match<_BiIter>& __lhs, const sub_match<_BiIter>& __rhs)
     ^~~~~~~~
/usr/include/c++/6/bits/regex.h:940:5: note:   template argument deduction/substitution failed:
/in/foo.cc:28:12: note:   'std::__cxx11::string {aka std::__cxx11::basic_string<char>}' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   if(a[0]=='A'){
            ^~~
In file included from /usr/include/c++/6/regex:62:0,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:110,
                 from /in/foo.cc:1:
/usr/include/c++/6/bits/regex.h:1013:5: note: candidate: template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::__cxx11::operator==(std::__cxx11::__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&, const std::__cxx11::sub_match<_BiIter>&)
     operator==(const __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>& __lhs,
     ^~~~~~~~
/usr/include/c++/6/bits/regex.h:1013:5: note:   template argument deduction/substitution failed:
/in/foo.cc:28:12: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'char'
   if(a[0]=='A'){
            ^~~
In file included from /usr/include/c++/6/regex:62:0,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:110,
                 from /in/foo.cc:1:
/usr/include/c++/6/bits/regex.h:1093:5: 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>&)
     operator==(const sub_match<_Bi_iter>& __lhs,
     ^~~~~~~~
/usr/include/c++/6/bits/regex.h:1093:5: note:   template argument deduction/substitution failed:
/in/foo.cc:28:12: note:   'std::__cxx11::string {aka std::__cxx11::basic_string<char>}' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   if(a[0]=='A'){
            ^~~
In file included from /usr/include/c++/6/regex:62:0,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:110,
                 from /in/foo.cc:1:
/usr/include/c++/6/bits/regex.h:1173:5: note: candidate: template<class _Bi_iter> bool std::__cxx11::operator==(const typename std::iterator_traits<_Iter>::value_type*, const std::__cxx11::sub_match<_BiIter>&)
     operator==(typename iterator_traits<_Bi_iter>::value_type const* __lhs,
     ^~~~~~~~
/usr/include/c++/6/bits/regex.h:1173:5: note:   template argument deduction/substitution failed:
/in/foo.cc:28:12: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'char'
   if(a[0]=='A'){
            ^~~
In file included from /usr/include/c++/6/regex:62:0,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:110,
                 from /in/foo.cc:1:
/usr/include/c++/6/bits/regex.h:1247:5: note: candidate: template<class _Bi_iter> bool std::__cxx11::operator==(const std::__cxx11::sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type*)
     operator==(const sub_match<_Bi_iter>& __lhs,
     ^~~~~~~~
/usr/include/c++/6/bits/regex.h:1247:5: note:   template argument deduction/substitution failed:
/in/foo.cc:28:12: note:   'std::__cxx11::string {aka std::__cxx11::basic_string<char>}' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   if(a[0]=='A'){
            ^~~
In file included from /usr/include/c++/6/regex:62:0,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:110,
                 from /in/foo.cc:1:
/usr/include/c++/6/bits/regex.h:1321:5: note: candidate: template<class _Bi_iter> bool std::__cxx11::operator==(const typename std::iterator_traits<_Iter>::value_type&, const std::__cxx11::sub_match<_BiIter>&)
     operator==(typename iterator_traits<_Bi_iter>::value_type const& __lhs,
     ^~~~~~~~
/usr/include/c++/6/bits/regex.h:1321:5: note:   template argument deduction/substitution failed:
/in/foo.cc:28:12: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'char'
   if(a[0]=='A'){
            ^~~
In file included from /usr/include/c++/6/regex:62:0,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:110,
                 from /in/foo.cc:1:
/usr/include/c++/6/bits/regex.h:1401:5: note: candidate: template<class _Bi_iter> bool std::__cxx11::operator==(const std::__cxx11::sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type&)
     operator==(const sub_match<_Bi_iter>& __lhs,
     ^~~~~~~~
/usr/include/c++/6/bits/regex.h:1401:5: note:   template argument deduction/substitution failed:
/in/foo.cc:28:12: note:   'std::__cxx11::string {aka std::__cxx11::basic_string<char>}' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   if(a[0]=='A'){
            ^~~
In file included from /usr/include/c++/6/regex:62:0,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:110,
                 from /in/foo.cc:1:
/usr/include/c++/6/bits/regex.h:1920:5: note: candidate: template<class _Bi_iter, class _Alloc> bool std::__cxx11::operator==(const std::__cxx11::match_results<_BiIter, _Alloc>&, const std::__cxx11::match_results<_BiIter, _Alloc>&)
     operator==(const match_results<_Bi_iter, _Alloc>& __m1,
     ^~~~~~~~
/usr/include/c++/6/bits/regex.h:1920:5: note:   template argument deduction/substitution failed:
/in/foo.cc:28:12: note:   'std::__cxx11::string {aka std::__cxx11::basic_string<char>}' is not derived from 'const std::__cxx11::match_results<_BiIter, _Alloc>'
   if(a[0]=='A'){
            ^~~
In file included from /usr/include/c++/6/iosfwd:40:0,
                 from /usr/include/c++/6/ios:38,
                 from /usr/include/c++/6/istream:38,
                 from /usr/include/c++/6/sstream:38,
                 from /usr/include/c++/6/complex:45,
                 from /usr/include/c++/6/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:52,
                 from /in/foo.cc:1:
/usr/include/c++/6/bits/postypes.h:216:5: note: candidate: template<class _StateT> bool std::operator==(const std::fpos<_StateT>&, const std::fpos<_StateT>&)
     operator==(const fpos<_StateT>& __lhs, const fpos<_StateT>& __rhs)
     ^~~~~~~~
/usr/include/c++/6/bits/postypes.h:216:5: note:   template argument deduction/substitution failed:
/in/foo.cc:28:12: note:   'std::__cxx11::string {aka std::__cxx11::basic_string<char>}' is not derived from 'const std::fpos<_StateT>'
   if(a[0]=='A'){
            ^~~
In file included from /usr/include/c++/6/bits/stl_algobase.h:64:0,
                 from /usr/include/c++/6/bits/char_traits.h:39,
                 from /usr/include/c++/6/ios:40,
                 from /usr/include/c++/6/istream:38,
                 from /usr/include/c++/6/sstream:38,
                 from /usr/include/c++/6/complex:45,
                 from /usr/include/c++/6/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:52,
                 from /in/foo.cc:1:
/usr/include/c++/6/bits/stl_pair.h:435:5: note: candidate: template<class _T1, class _T2> constexpr bool std::operator==(const std::pair<_T1, _T2>&, const std::pair<_T1, _T2>&)
     operator==(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
     ^~~~~~~~
/usr/include/c++/6/bits/stl_pair.h:435:5: note:   template argument deduction/substitution failed:
/in/foo.cc:28:12: note:   'std::__cxx11::string {aka std::__cxx11::basic_string<char>}' is not derived from 'const