Language: C++

#include <iostream>
 
using namespace std;
 
int main(){
	string S;
 	cout << S;
	bool isOk = true;
  
  	for (int i = 0; i < S.length();i++){
    	if(i%2 == 0){
          if(std::equal(S[i], string("R"))){
              isOK = false;
          }
        }else
        {
        	if(std::equal(S[ai], string("L"))){
              isOK = false;
          }
        }
    }
  	if(isOK){
    	cout<<"Yes";
    }else{
    	cout <<"No";
    }
}

Compiler output:
a.cc: In function 'int main()':
a.cc:12:24: error: no matching function for call to 'equal(__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type&, std::string)'
   12 |           if(std::equal(S[i], string("R"))){
      |              ~~~~~~~~~~^~~~~~~~~~~~~~~~~~~
In file included from /usr/include/c++/14/string:51,
                 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,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_algobase.h:1582:5: note: candidate: 'template<class _II1, class _II2> bool std::equal(_II1, _II1, _II2)'
 1582 |     equal(_II1 __first1, _II1 __last1, _II2 __first2)
      |     ^~~~~
/usr/include/c++/14/bits/stl_algobase.h:1582:5: note:   candidate expects 3 arguments, 2 provided
/usr/include/c++/14/bits/stl_algobase.h:1613:5: note: candidate: 'template<class _IIter1, class _IIter2, class _BinaryPredicate> bool std::equal(_IIter1, _IIter1, _IIter2, _BinaryPredicate)'
 1613 |     equal(_IIter1 __first1, _IIter1 __last1,
      |     ^~~~~
/usr/include/c++/14/bits/stl_algobase.h:1613:5: note:   candidate expects 4 arguments, 2 provided
/usr/include/c++/14/bits/stl_algobase.h:1704:5: note: candidate: 'template<class _II1, class _II2> bool std::equal(_II1, _II1, _II2, _II2)'
 1704 |     equal(_II1 __first1, _II1 __last1, _II2 __first2, _II2 __last2)
      |     ^~~~~
/usr/include/c++/14/bits/stl_algobase.h:1704:5: note:   candidate expects 4 arguments, 2 provided
/usr/include/c++/14/bits/stl_algobase.h:1737:5: note: candidate: 'template<class _IIter1, class _IIter2, class _BinaryPredicate> bool std::equal(_IIter1, _IIter1, _IIter2, _IIter2, _BinaryPredicate)'
 1737 |     equal(_IIter1 __first1, _IIter1 __last1,
      |     ^~~~~
/usr/include/c++/14/bits/stl_algobase.h:1737:5: note:   candidate expects 5 arguments, 2 provided
a.cc:13:15: error: 'isOK' was not declared in this scope; did you mean 'isOk'?
   13 |               isOK = false;
      |               ^~~~
      |               isOk
a.cc:17:33: error: 'ai' was not declared in this scope; did you mean 'i'?
   17 |                 if(std::equal(S[ai], string("L"))){
      |                                 ^~
      |                                 i
a.cc:18:15: error: 'isOK' was not declared in this scope; did you mean 'isOk'?
   18 |               isOK = false;
      |               ^~~~
      |               isOk
a.cc:22:12: error: 'isOK' was not declared in this scope; did you mean 'isOk'?
   22 |         if(isOK){
      |            ^~~~
      |            isOk