Language: C++

#include<bits/stdc++.h>
#define MOD 1000000007

#define DEBUG 1
#define ONLINE_JUDGE 0

/* -------------------This is the part you need to copy ----------------------*/
#if DEBUG && !ONLINE_JUDGE
    template<typename T>
    inline std::ostream &operator << (std::ostream & os,const std::vector<T>& v);
    template<typename T>
    inline std::ostream &operator << (std::ostream & os,const std::set<T>& v);
    template <typename T1, typename T2>
    inline std::ostream& operator << (std::ostream& os, const std::pair<T1, T2>& p);
    template<typename T1, typename T2>
    inline std::ostream &operator << (std::ostream & os,const std::map<T1, T2>& v);
    #define debug(args...)     (Debugger()) , args
 
    class Debugger
    {
        public:
        Debugger(const std::string& _separator = ", ") :
        first(true), separator(_separator){}
        
        template<typename ObjectType>
        Debugger& operator , (const ObjectType& v)
        {
            if(!first)
                std::cout << separator;
            std::cout << v;
            first = false;
            return *this;
        }
        ~Debugger() {  std::cout << endl;}
        
        private:
        bool first;
        std::string separator;
    };
 
    template <typename T1, typename T2>
    inline std::ostream& operator << (std::ostream& os, const std::pair<T1, T2>& p)
    {
        return os << "(" << p.first << ", " << p.second << ")";
    }
 
    template<typename T>
    inline std::ostream &operator << (std::ostream & os,const std::vector<T>& v)
    {
        bool first = true;
        os << "[";
        for(unsigned int i = 0; i < v.size(); i++)
        {
            if(!first)
                os << ", ";
            os << v[i];
            first = false;
        }
        return os << "]";
    }
 
    template<typename T>
    inline std::ostream &operator << (std::ostream & os,const std::set<T>& v)
    {
        bool first = true;
        os << "[";
        for (typename std::set<T>::const_iterator ii = v.begin(); ii != v.end(); ++ii)
        {
            if(!first)
                os << ", ";
            os << *ii;
            first = false;
        }
        return os << "]";
    }
 
    template<typename T1, typename T2>
    inline std::ostream &operator << (std::ostream & os,const std::map<T1, T2>& v)
    {
        bool first = true;
        os << "[";
        for (typename std::map<T1, T2>::const_iterator ii = v.begin(); ii != v.end(); ++ii)
        {
            if(!first)
                os << ", ";
            os << *ii ;
            first = false;
        }
        return os << "]";
    }
    
#else
    #define debug(args...)                  // Just strip off all debug tokens
#endif 
/*-------------------------------Stop here---------------------------------*/
using namespace std;
typedef unsigned int uint;
typedef unsigned long int lu;
typedef unsigned long long llu;
typedef long int ld;
typedef long long lld;
typedef vector<int> vint;
typedef vector<unsigned int> vuint;
typedef vector<unsigned long int> vlu;
typedef vector<unsigned long long> vllu;
typedef vector<long int> vld;
typedef vector<long long> vlld;

int main()          
{
    char c;
    cin>>c;
    if((int)'a'<= c && c <= (int)'z')
        cout<<'a'<<endl;
    else if((int)'A' <=c && c<= (int)'Z')
        cout<<'A'<<endl;
    return 0;
}


Compiler output:
a.cc: In destructor 'Debugger::~Debugger()':
a.cc:34:37: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   34 |         ~Debugger() {  std::cout << endl;}
      |                                     ^~~~
      |                                     std::endl
In file included from /usr/include/c++/14/istream:41,
                 from /usr/include/c++/14/sstream:40,
                 from /usr/include/c++/14/complex:45,
                 from /usr/include/c++/14/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:127,
                 from a.cc:1:
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~