Language: C++

#include <iostream>
using namespace std;

#define PrintLn(X) cout << X << endl
#define Rep(i, n) for(int i = 0; i < (int)(n); ++i)

int main(void)
{
	char a, b;
	cin >> a >> b;
	PrintLn(a == b ? 'H' : 'D');
	return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:11:19: error: no match for 'operator==' (operand types are 'std::basic_ostream<char>' and 'char')
   11 |         PrintLn(a == b ? 'H' : 'D');
      |                   ^~ ~
      |                      |
      |                      char
a.cc:4:28: note: in definition of macro 'PrintLn'
    4 | #define PrintLn(X) cout << X << endl
      |                            ^
a.cc:11:19: note: candidate: 'operator==(int, int)' (built-in)
   11 |         PrintLn(a == b ? 'H' : 'D');
      |                   ^
a.cc:4:28: note: in definition of macro 'PrintLn'
    4 | #define PrintLn(X) cout << X << endl
      |                            ^
a.cc:11:19: note:   no known conversion for argument 1 from 'std::basic_ostream<char>' to 'int'
   11 |         PrintLn(a == b ? 'H' : 'D');
      |                   ^
a.cc:4:28: note: in definition of macro 'PrintLn'
    4 | #define PrintLn(X) cout << X << endl
      |                            ^
In file included from /usr/include/c++/14/iosfwd:42,
                 from /usr/include/c++/14/ios:40,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:1:
/usr/include/c++/14/bits/postypes.h:192:5: note: candidate: 'template<class _StateT> bool std::operator==(const fpos<_StateT>&, const fpos<_StateT>&)'
  192 |     operator==(const fpos<_StateT>& __lhs, const fpos<_StateT>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/postypes.h:192:5: note:   template argument deduction/substitution failed:
a.cc:11:22: note:   'std::basic_ostream<char>' is not derived from 'const std::fpos<_StateT>'
   11 |         PrintLn(a == b ? 'H' : 'D');
      |                      ^
a.cc:4:28: note: in definition of macro 'PrintLn'
    4 | #define PrintLn(X) cout << X << endl
      |                            ^
In file included from /usr/include/c++/14/string:43,
                 from /usr/include/c++/14/bits/locale_classes.h:40,
                 from /usr/include/c++/14/bits/ios_base.h:41,
                 from /usr/include/c++/14/ios:44:
/usr/include/c++/14/bits/allocator.h:235:5: note: candidate: 'template<class _T1, class _T2> bool std::operator==(const allocator<_CharT>&, const allocator<_T2>&)'
  235 |     operator==(const allocator<_T1>&, const allocator<_T2>&)
      |     ^~~~~~~~
/usr/include/c++/14/bits/allocator.h:235:5: note:   template argument deduction/substitution failed:
a.cc:11:22: note:   'std::basic_ostream<char>' is not derived from 'const std::allocator<_CharT>'
   11 |         PrintLn(a == b ? 'H' : 'D');
      |                      ^
a.cc:4:28: note: in definition of macro 'PrintLn'
    4 | #define PrintLn(X) cout << X << endl
      |                            ^
In file included from /usr/include/c++/14/string:48:
/usr/include/c++/14/bits/stl_iterator.h:441:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator==(const reverse_iterator<_Iterator>&, const reverse_iterator<_Iterator>&)'
  441 |     operator==(const reverse_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:441:5: note:   template argument deduction/substitution failed:
a.cc:11:22: note:   'std::basic_ostream<char>' is not derived from 'const std::reverse_iterator<_Iterator>'
   11 |         PrintLn(a == b ? 'H' : 'D');
      |                      ^
a.cc:4:28: note: in definition of macro 'PrintLn'
    4 | #define PrintLn(X) cout << X << endl
      |                            ^
/usr/include/c++/14/bits/stl_iterator.h:486:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator==(const reverse_iterator<_Iterator>&, const reverse_iterator<_IteratorR>&)'
  486 |     operator==(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:486:5: note:   template argument deduction/substitution failed:
a.cc:11:22: note:   'std::basic_ostream<char>' is not derived from 'const std::reverse_iterator<_Iterator>'
   11 |         PrintLn(a == b ? 'H' : 'D');
      |                      ^
a.cc:4:28: note: in definition of macro 'PrintLn'
    4 | #define PrintLn(X) cout << X << endl
      |                            ^
/usr/include/c++/14/bits/stl_iterator.h:1667:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator==(const move_iterator<_IteratorL>&, const move_iterator<_IteratorR>&)'
 1667 |     operator==(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1667:5: note:   template argument deduction/substitution failed:
a.cc:11:22: note:   'std::basic_ostream<char>' is not derived from 'const std::move_iterator<_IteratorL>'
   11 |         PrintLn(a == b ? 'H' : 'D');
      |                      ^
a.cc:4:28: note: in definition of macro 'PrintLn'
    4 | #define PrintLn(X) cout << X << endl
      |                            ^
/usr/include/c++/14/bits/stl_iterator.h:1737:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator==(const move_iterator<_IteratorL>&, const move_iterator<_IteratorL>&)'
 1737 |     operator==(const move_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1737:5: note:   template argument deduction/substitution failed:
a.cc:11:22: note:   'std::basic_ostream<char>' is not derived from 'const std::move_iterator<_IteratorL>'
   11 |         PrintLn(a == b ? 'H' : 'D');
      |                      ^
a.cc:4:28: note: in definition of macro 'PrintLn'
    4 | #define PrintLn(X) cout << X << endl
      |                            ^
In file included from /usr/include/c++/14/bits/stl_algobase.h:64,
                 from /usr/include/c++/14/string:51:
/usr/include/c++/14/bits/stl_pair.h:1033:5: note: candidate: 'template<class _T1, class _T2> constexpr bool std::operator==(const pair<_T1, _T2>&, const pair<_T1, _T2>&)'
 1033 |     operator==(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:1033:5: note:   template argument deduction/substitution failed:
a.cc:11:22: note:   'std::basic_ostream<char>' is not derived from 'const std::pair<_T1, _T2>'
   11 |         PrintLn(a == b ? 'H' : 'D');
      |                      ^
a.cc:4:28: note: in definition of macro 'PrintLn'
    4 | #define PrintLn(X) cout << X << endl
      |                            ^
In file included from /usr/include/c++/14/bits/basic_string.h:47,
                 from /usr/include/c++/14/string:54:
/usr/include/c++/14/string_view:629:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator==(basic_string_view<_CharT, _Traits>, __type_identity_t<basic_string_view<_CharT, _Traits> >)'
  629 |     operator==(basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:629:5: note:   template argument deduction/substitution failed:
a.cc:11:22: note:   'std::basic_ostream<char>' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   11 |         PrintLn(a == b ? 'H' : 'D');
      |                      ^
a.cc:4:28: note: in definition of macro 'PrintLn'
    4 | #define PrintLn(X) cout << X << endl
      |                            ^
/usr/include/c++/14/string_view:637:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator==(basic_string_view<_CharT, _Traits>, basic_string_view<_CharT, _Traits>)'
  637 |     operator==(basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:637:5: note:   template argument deduction/substitution failed:
a.cc:11:22: note:   'std::basic_ostream<char>' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   11 |         PrintLn(a == b ? 'H' : 'D');
      |                      ^
a.cc:4:28: note: in definition of macro 'PrintLn'
    4 | #define PrintLn(X) cout << X << endl
      |                            ^
/usr/include/c++/14/string_view:644:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator==(__type_identity_t<basic_string_view<_CharT, _Traits> >, basic_string_view<_CharT, _Traits>)'
  644 |     operator==(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:644:5: note:   template argument deduction/substitution failed:
a.cc:11:22: note:   mismatched types 'std::basic_string_view<_CharT, _Traits>' and 'char'
   11 |         PrintLn(a == b ? 'H' : 'D');
      |                      ^
a.cc:4:28: note: in definition of macro 'PrintLn'
    4 | #define PrintLn(X) cout << X << endl
      |                            ^
/usr/include/c++/14/bits/basic_string.h:3755:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator==(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3755 |     operator==(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3755:5: note:   template argument deduction/substitution failed:
a.cc:11:22: note:   'std::basic_ostream<char>' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   11 |         PrintLn(a == b ? 'H' : 'D');
      |                      ^
a.cc:4:28: note: in definition of macro 'PrintLn'
    4 | #define PrintLn(X) cout << X << endl
      |                            ^
/usr/include/c++/14/bits/basic_string.h:3772:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator==(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, const _CharT*)'
 3772 |     operator==(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3772:5: note:   template argument deduction/substitution failed:
a.cc:11:22: note:   'std::basic_ostream<char>' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   11 |         PrintLn(a == b ? 'H' : 'D');
      |                      ^
a.cc:4:28: note: in definition of macro 'PrintLn'
    4 | #define PrintLn(X) cout << X << endl
      |                            ^
/usr/inc