Language: C++

#include <bits/stdc++.h>
using namespace std;
template <typename T>
bool PN(T x)
{
  if (x <= 1)
    return false;
  if (x == 2)
    return true;
  for (int i = 2; i < sqrt(x) + 1; i++)
    if (x % i == 0)
      return false;
  return true;
}

const long long MOD = 1e9+7;

void solve()
{
  string a, b; cin >> a >> b;
  int asize = a.size(), bsize = b.size();
  if(asize > bsize) cout << "GREATER" << endl;
  else if(asize < bsize) cout << "LESS" << endl;
  else cout << "EQUAL" << endl;
  int i = 0;
  while(1){
    if(stoi(a[i]) > stoi(b[i])) {
      cout << "GREATER" << endl;
      return;
    } else if(stoi(a[i]) < stoi(b[i])){
      cout <<"LESS"  << endl;
      return;
    } else {
      i++;
    }
  }

}

int main()
{
  solve();
  return 0;
}

Compiler output:
a.cc: In function 'void solve()':
a.cc:27:12: error: no matching function for call to 'stoi(__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type&)'
   27 |     if(stoi(a[i]) > stoi(b[i])) {
      |        ~~~~^~~~~~
In file included 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,
                 from a.cc:1:
/usr/include/c++/14/bits/basic_string.h:4164:3: note: candidate: 'int std::__cxx11::stoi(const std::string&, std::size_t*, int)'
 4164 |   stoi(const string& __str, size_t* __idx = 0, int __base = 10)
      |   ^~~~
/usr/include/c++/14/bits/basic_string.h:4164:22: note:   no known conversion for argument 1 from '__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type' {aka 'char'} to 'const std::string&' {aka 'const std::__cxx11::basic_string<char>&'}
 4164 |   stoi(const string& __str, size_t* __idx = 0, int __base = 10)
      |        ~~~~~~~~~~~~~~^~~~~
/usr/include/c++/14/bits/basic_string.h:4432:3: note: candidate: 'int std::__cxx11::stoi(const std::wstring&, std::size_t*, int)'
 4432 |   stoi(const wstring& __str, size_t* __idx = 0, int __base = 10)
      |   ^~~~
/usr/include/c++/14/bits/basic_string.h:4432:23: note:   no known conversion for argument 1 from '__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type' {aka 'char'} to 'const std::wstring&' {aka 'const std::__cxx11::basic_string<wchar_t>&'}
 4432 |   stoi(const wstring& __str, size_t* __idx = 0, int __base = 10)
      |        ~~~~~~~~~~~~~~~^~~~~
a.cc:27:25: error: no matching function for call to 'stoi(__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type&)'
   27 |     if(stoi(a[i]) > stoi(b[i])) {
      |                     ~~~~^~~~~~
/usr/include/c++/14/bits/basic_string.h:4164:3: note: candidate: 'int std::__cxx11::stoi(const std::string&, std::size_t*, int)'
 4164 |   stoi(const string& __str, size_t* __idx = 0, int __base = 10)
      |   ^~~~
/usr/include/c++/14/bits/basic_string.h:4164:22: note:   no known conversion for argument 1 from '__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type' {aka 'char'} to 'const std::string&' {aka 'const std::__cxx11::basic_string<char>&'}
 4164 |   stoi(const string& __str, size_t* __idx = 0, int __base = 10)
      |        ~~~~~~~~~~~~~~^~~~~
/usr/include/c++/14/bits/basic_string.h:4432:3: note: candidate: 'int std::__cxx11::stoi(const std::wstring&, std::size_t*, int)'
 4432 |   stoi(const wstring& __str, size_t* __idx = 0, int __base = 10)
      |   ^~~~
/usr/include/c++/14/bits/basic_string.h:4432:23: note:   no known conversion for argument 1 from '__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type' {aka 'char'} to 'const std::wstring&' {aka 'const std::__cxx11::basic_string<wchar_t>&'}
 4432 |   stoi(const wstring& __str, size_t* __idx = 0, int __base = 10)
      |        ~~~~~~~~~~~~~~~^~~~~
a.cc:30:19: error: no matching function for call to 'stoi(__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type&)'
   30 |     } else if(stoi(a[i]) < stoi(b[i])){
      |               ~~~~^~~~~~
/usr/include/c++/14/bits/basic_string.h:4164:3: note: candidate: 'int std::__cxx11::stoi(const std::string&, std::size_t*, int)'
 4164 |   stoi(const string& __str, size_t* __idx = 0, int __base = 10)
      |   ^~~~
/usr/include/c++/14/bits/basic_string.h:4164:22: note:   no known conversion for argument 1 from '__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type' {aka 'char'} to 'const std::string&' {aka 'const std::__cxx11::basic_string<char>&'}
 4164 |   stoi(const string& __str, size_t* __idx = 0, int __base = 10)
      |        ~~~~~~~~~~~~~~^~~~~
/usr/include/c++/14/bits/basic_string.h:4432:3: note: candidate: 'int std::__cxx11::stoi(const std::wstring&, std::size_t*, int)'
 4432 |   stoi(const wstring& __str, size_t* __idx = 0, int __base = 10)
      |   ^~~~
/usr/include/c++/14/bits/basic_string.h:4432:23: note:   no known conversion for argument 1 from '__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type' {aka 'char'} to 'const std::wstring&' {aka 'const std::__cxx11::basic_string<wchar_t>&'}
 4432 |   stoi(const wstring& __str, size_t* __idx = 0, int __base = 10)
      |        ~~~~~~~~~~~~~~~^~~~~
a.cc:30:32: error: no matching function for call to 'stoi(__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type&)'
   30 |     } else if(stoi(a[i]) < stoi(b[i])){
      |                            ~~~~^~~~~~
/usr/include/c++/14/bits/basic_string.h:4164:3: note: candidate: 'int std::__cxx11::stoi(const std::string&, std::size_t*, int)'
 4164 |   stoi(const string& __str, size_t* __idx = 0, int __base = 10)
      |   ^~~~
/usr/include/c++/14/bits/basic_string.h:4164:22: note:   no known conversion for argument 1 from '__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type' {aka 'char'} to 'const std::string&' {aka 'const std::__cxx11::basic_string<char>&'}
 4164 |   stoi(const string& __str, size_t* __idx = 0, int __base = 10)
      |        ~~~~~~~~~~~~~~^~~~~
/usr/include/c++/14/bits/basic_string.h:4432:3: note: candidate: 'int std::__cxx11::stoi(const std::wstring&, std::size_t*, int)'
 4432 |   stoi(const wstring& __str, size_t* __idx = 0, int __base = 10)
      |   ^~~~
/usr/include/c++/14/bits/basic_string.h:4432:23: note:   no known conversion for argument 1 from '__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type' {aka 'char'} to 'const std::wstring&' {aka 'const std::__cxx11::basic_string<wchar_t>&'}
 4432 |   stoi(const wstring& __str, size_t* __idx = 0, int __base = 10)
      |        ~~~~~~~~~~~~~~~^~~~~