Main.cc: In function ‘int main()’:
Main.cc:8:10: error: no match for ‘operator<’ (operand types are ‘std::ostream’ {aka ‘std::basic_ostream’} and ‘const char [6]’)
cout<"b 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++/8/bits/stl_pair.h:454:5: note: template argument deduction/substitution failed:
Main.cc:8:11: note: ‘std::ostream’ {aka ‘std::basic_ostream’} is not derived from ‘const std::pair<_T1, _T2>’
cout<"b