Language: C++

#include<bits/stdc++.h>
using namespace std;
int main()
{string a,b;cin>>a>>b;
if(a<=1&&a[0]!=0&&b[0]!=0)
{
if(a>b)
cout<<"greater";
if(a<b)
cout<<"less";

if(a==b)
cout<<"equal";
}
return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:5:5: error: no match for 'operator<=' (operand types are 'std::string' {aka 'std::__cxx11::basic_string<char>'} and 'int')
    5 | if(a<=1&&a[0]!=0&&b[0]!=0)
      |    ~^~~
      |    |  |
      |    |  int
      |    std::string {aka std::__cxx11::basic_string<char>}
In file included from /usr/include/c++/14/regex:68,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:181,
                 from a.cc:1:
/usr/include/c++/14/bits/regex.h:1154:5: note: candidate: 'template<class _BiIter> bool std::__cxx11::operator<=(const sub_match<_BiIter>&, const sub_match<_BiIter>&)'
 1154 |     operator<=(const sub_match<_BiIter>& __lhs, const sub_match<_BiIter>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1154:5: note:   template argument deduction/substitution failed:
a.cc:5:7: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
    5 | if(a<=1&&a[0]!=0&&b[0]!=0)
      |       ^
/usr/include/c++/14/bits/regex.h:1260:5: note: candidate: 'template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::__cxx11::operator<=(__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&, const sub_match<_BiIter>&)'
 1260 |     operator<=(const __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1260:5: note:   template argument deduction/substitution failed:
a.cc:5:7: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'int'
    5 | if(a<=1&&a[0]!=0&&b[0]!=0)
      |       ^
/usr/include/c++/14/bits/regex.h:1353:5: note: candidate: 'template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::__cxx11::operator<=(const sub_match<_BiIter>&, __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&)'
 1353 |     operator<=(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1353:5: note:   template argument deduction/substitution failed:
a.cc:5:7: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
    5 | if(a<=1&&a[0]!=0&&b[0]!=0)
      |       ^
/usr/include/c++/14/bits/regex.h:1427:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator<=(const typename std::iterator_traits<_Iter>::value_type*, const sub_match<_BiIter>&)'
 1427 |     operator<=(typename iterator_traits<_Bi_iter>::value_type const* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1427:5: note:   template argument deduction/substitution failed:
a.cc:5:7: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'int'
    5 | if(a<=1&&a[0]!=0&&b[0]!=0)
      |       ^
/usr/include/c++/14/bits/regex.h:1521:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator<=(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type*)'
 1521 |     operator<=(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1521:5: note:   template argument deduction/substitution failed:
a.cc:5:7: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
    5 | if(a<=1&&a[0]!=0&&b[0]!=0)
      |       ^
/usr/include/c++/14/bits/regex.h:1599:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator<=(const typename std::iterator_traits<_Iter>::value_type&, const sub_match<_BiIter>&)'
 1599 |     operator<=(typename iterator_traits<_Bi_iter>::value_type const& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1599:5: note:   template argument deduction/substitution failed:
a.cc:5:7: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'int'
    5 | if(a<=1&&a[0]!=0&&b[0]!=0)
      |       ^
/usr/include/c++/14/bits/regex.h:1699:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator<=(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type&)'
 1699 |     operator<=(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1699:5: note:   template argument deduction/substitution failed:
a.cc:5:7: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
    5 | if(a<=1&&a[0]!=0&&b[0]!=0)
      |       ^
In file included from /usr/include/c++/14/bits/stl_algobase.h:64,
                 from /usr/include/c++/14/algorithm:60,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51:
/usr/include/c++/14/bits/stl_pair.h:1064:5: note: candidate: 'template<class _T1, class _T2> constexpr bool std::operator<=(const pair<_T1, _T2>&, const pair<_T1, _T2>&)'
 1064 |     operator<=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:1064:5: note:   template argument deduction/substitution failed:
a.cc:5:7: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::pair<_T1, _T2>'
    5 | if(a<=1&&a[0]!=0&&b[0]!=0)
      |       ^
In file included from /usr/include/c++/14/bits/stl_algobase.h:67:
/usr/include/c++/14/bits/stl_iterator.h:469:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator<=(const reverse_iterator<_Iterator>&, const reverse_iterator<_Iterator>&)'
  469 |     operator<=(const reverse_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:469:5: note:   template argument deduction/substitution failed:
a.cc:5:7: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::reverse_iterator<_Iterator>'
    5 | if(a<=1&&a[0]!=0&&b[0]!=0)
      |       ^
/usr/include/c++/14/bits/stl_iterator.h:513:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator<=(const reverse_iterator<_Iterator>&, const reverse_iterator<_IteratorR>&)'
  513 |     operator<=(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:513:5: note:   template argument deduction/substitution failed:
a.cc:5:7: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::reverse_iterator<_Iterator>'
    5 | if(a<=1&&a[0]!=0&&b[0]!=0)
      |       ^
/usr/include/c++/14/bits/stl_iterator.h:1704:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator<=(const move_iterator<_IteratorL>&, const move_iterator<_IteratorR>&)'
 1704 |     operator<=(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1704:5: note:   template argument deduction/substitution failed:
a.cc:5:7: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::move_iterator<_IteratorL>'
    5 | if(a<=1&&a[0]!=0&&b[0]!=0)
      |       ^
/usr/include/c++/14/bits/stl_iterator.h:1767:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator<=(const move_iterator<_IteratorL>&, const move_iterator<_IteratorL>&)'
 1767 |     operator<=(const move_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1767:5: note:   template argument deduction/substitution failed:
a.cc:5:7: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::move_iterator<_IteratorL>'
    5 | if(a<=1&&a[0]!=0&&b[0]!=0)
      |       ^
In file included from /usr/include/c++/14/bits/basic_string.h:47,
                 from /usr/include/c++/14/string:54,
                 from /usr/include/c++/14/bitset:52,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:52:
/usr/include/c++/14/string_view:717:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator<=(basic_string_view<_CharT, _Traits>, basic_string_view<_CharT, _Traits>)'
  717 |     operator<=(basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:717:5: note:   template argument deduction/substitution failed:
a.cc:5:7: note:   'std::__cxx11::basic_string<char>' is not derived from 'std::basic_string_view<_CharT, _Traits>'
    5 | if(a<=1&&a[0]!=0&&b[0]!=0)
      |       ^
/usr/include/c++/14/string_view:724:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator<=(basic_string_view<_CharT, _Traits>, __type_identity_t<basic_string_view<_CharT, _Traits> >)'
  724 |     operator<=(basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:724:5: note:   template argument deduction/substitution failed:
a.cc:5:7: note:   'std::__cxx11::basic_string<char>' is not derived from 'std::basic_string_view<_CharT, _Traits>'
    5 | if(a<=1&&a[0]!=0&&b[0]!=0)
      |       ^
/usr/include/c++/14/string_view:732:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator<=(__type_identity_t<basic_string_view<_CharT, _Traits> >, basic_string_view<_CharT, _Traits>)'
  732 |     operator<=(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:732:5: note:   template argument deduction/substitution failed:
a.cc:5:7: note:   mismatched types 'std::basic_string_view<_CharT, _Traits>' and 'int'
    5 | if(a<=1&&a[0]!=0&&b[0]!=0)
      |       ^
/usr/include/c++/14/bits/basic_string.h:3956:5: 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>&)'
 3956 |     operator<=(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3956:5: note:   template argument deduction/substitution failed:
a.cc:5:7: note:   mismatched types 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>' and 'int'
    5 | if(a<=1&&a[0]!=0&&b[0]!=0)
      |       ^
/usr/include/c++/14/bits/basic_string.h:3970:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator<=(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, const _Ch