Language: C++

#include<iostream>
using namespace std;


#define f(i,a,b) for(int i=(int)(a);i<=(int)(b);i++)
#define char_f(i,a) for(int i=(int)(a);(char)s[i]!='\0';i++)
#define rf(i,a,b) for(int i=(int)(a);i>=(int)(b);i--)
#define llf(i,a,b) for(long long int i=(long long int)(a);i<=(long long int)(b);i++)
#define llrf(i,a,b) for(long long int i=(long long int)(b);i>=(long long int)(a);i--)



#define ll long long
#define fi first
#define se second
#define pb push_back
#define pop pop_back
#define mem(ara) memset((ara),0,sizeof(ara))
#define memn(ara) memset((ara),-1,sizeof(ara))
#define b begin()
#define e end()
#define em emplace
#define eb emplace_back





#define si set<int>
#define sd set<double>
#define sll set<long long int>
#define ss set<string>
#define sc set<char>

#define pii pair<int,int>
#define pli pair<long long int,int>
#define pil pair<int,long long int>
#define pll pair<long long int,long long int>
#define pci pair<char,int>
#define pic pair<int,char>
#define pcl pair<char,long long int>
#define plc pair<long long int,char>

#define pss pair<string,string>
#define pcc pair<char,char>

#define pis pair<int,string>
#define psi pair<string,int>
#define pls pair<long long int,string>
#define psl pair<string,long long int>
#define pdd pair<double,double>
#define pcs pair<char,string>
#define psc pair<string,char>



#define vi  vector<int>
#define vll vector<long long int>
#define vd vector<double>
#define vs vector<string>
#define vc vector<char>
#define vii vector<pii>



#define mod 1000000007
#define mx (1<<30)-1
#define llmx (1ll<<62)
#define n_size 100005
#define g_size 10000005
double PI=acos(-1);



///unsigned int uMAX=4294967295;
///unsigned ll int ullMAX=18446744073709551615;





int arr[g_size];



int main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(nullptr);
	cout.tie(nullptr);

	int n,m,T,res;

	int maxi=-mx,mini=mx,count=0;

    	int i,j,k;

	bool flag;

	string s1,s2;

	char s[100000],a,b;

	int ara[n_size],ara2[n_size];
	
	cin>>a>>b;
	
	if(a=='H') {
        if(b=='H') cout<<"H"<<endl;
        if(b=='D') cout<<"D"<<endl;
	}
	else if(a=='D') {
        if(b=='H') cout<<"D"<<endl;
        if(b=='D') cout<<"H"<<endl;
	}	
	
	
}


Compiler output:
a.cc:71:11: error: 'acos' was not declared in this scope
   71 | double PI=acos(-1);
      |           ^~~~
a.cc: In function 'int main()':
a.cc:20:16: warning: empty parentheses were disambiguated as a function declaration [-Wvexing-parse]
   20 | #define b begin()
      |                ^~
a.cc:102:26: note: in expansion of macro 'b'
  102 |         char s[100000],a,b;
      |                          ^
a.cc:20:16: note: remove parentheses to default-initialize a variable
   20 | #define b begin()
      |                ^~
a.cc:102:26: note: in expansion of macro 'b'
  102 |         char s[100000],a,b;
      |                          ^
a.cc:20:16: note: or replace parentheses with braces to value-initialize a variable
   20 | #define b begin()
      |                ^~
a.cc:102:26: note: in expansion of macro 'b'
  102 |         char s[100000],a,b;
      |                          ^
a.cc:106:15: error: no match for 'operator>>' (operand types are 'std::basic_istream<char>' and 'char')
  106 |         cin>>a>>b;
      |         ~~~~~~^~
      |            |
      |            std::basic_istream<char>
In file included from /usr/include/c++/14/iostream:42,
                 from a.cc:1:
/usr/include/c++/14/istream:170:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(bool&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  170 |       operator>>(bool& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:170:7: note:   conversion of argument 1 would be ill-formed:
a.cc:20:16: error: cannot bind non-const lvalue reference of type 'bool&' to a value of type 'char'
   20 | #define b begin()
      |           ~~~~~^~
a.cc:106:17: note: in expansion of macro 'b'
  106 |         cin>>a>>b;
      |                 ^
/usr/include/c++/14/istream:174:7: note: candidate: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(short int&) [with _CharT = char; _Traits = std::char_traits<char>]' (near match)
  174 |       operator>>(short& __n);
      |       ^~~~~~~~
/usr/include/c++/14/istream:174:7: note:   conversion of argument 1 would be ill-formed:
a.cc:20:16: error: cannot bind non-const lvalue reference of type 'short int&' to a value of type 'char'
   20 | #define b begin()
      |           ~~~~~^~
a.cc:106:17: note: in expansion of macro 'b'
  106 |         cin>>a>>b;
      |                 ^
/usr/include/c++/14/istream:177:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(short unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  177 |       operator>>(unsigned short& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:177:7: note:   conversion of argument 1 would be ill-formed:
a.cc:20:16: error: cannot bind non-const lvalue reference of type 'short unsigned int&' to a value of type 'char'
   20 | #define b begin()
      |           ~~~~~^~
a.cc:106:17: note: in expansion of macro 'b'
  106 |         cin>>a>>b;
      |                 ^
/usr/include/c++/14/istream:181:7: note: candidate: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(int&) [with _CharT = char; _Traits = std::char_traits<char>]' (near match)
  181 |       operator>>(int& __n);
      |       ^~~~~~~~
/usr/include/c++/14/istream:181:7: note:   conversion of argument 1 would be ill-formed:
a.cc:20:16: error: cannot bind non-const lvalue reference of type 'int&' to a value of type 'char'
   20 | #define b begin()
      |           ~~~~~^~
a.cc:106:17: note: in expansion of macro 'b'
  106 |         cin>>a>>b;
      |                 ^
/usr/include/c++/14/istream:184:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  184 |       operator>>(unsigned int& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:184:7: note:   conversion of argument 1 would be ill-formed:
a.cc:20:16: error: cannot bind non-const lvalue reference of type 'unsigned int&' to a value of type 'char'
   20 | #define b begin()
      |           ~~~~~^~
a.cc:106:17: note: in expansion of macro 'b'
  106 |         cin>>a>>b;
      |                 ^
/usr/include/c++/14/istream:188:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  188 |       operator>>(long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:188:7: note:   conversion of argument 1 would be ill-formed:
a.cc:20:16: error: cannot bind non-const lvalue reference of type 'long int&' to a value of type 'char'
   20 | #define b begin()
      |           ~~~~~^~
a.cc:106:17: note: in expansion of macro 'b'
  106 |         cin>>a>>b;
      |                 ^
/usr/include/c++/14/istream:192:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  192 |       operator>>(unsigned long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:192:7: note:   conversion of argument 1 would be ill-formed:
a.cc:20:16: error: cannot bind non-const lvalue reference of type 'long unsigned int&' to a value of type 'char'
   20 | #define b begin()
      |           ~~~~~^~
a.cc:106:17: note: in expansion of macro 'b'
  106 |         cin>>a>>b;
      |                 ^
/usr/include/c++/14/istream:199:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  199 |       operator>>(long long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:199:7: note:   conversion of argument 1 would be ill-formed:
a.cc:20:16: error: cannot bind non-const lvalue reference of type 'long long int&' to a value of type 'char'
   20 | #define b begin()
      |           ~~~~~^~
a.cc:106:17: note: in expansion of macro 'b'
  106 |         cin>>a>>b;
      |                 ^
/usr/include/c++/14/istream:203:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  203 |       operator>>(unsigned long long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:203:7: note:   conversion of argument 1 would be ill-formed:
a.cc:20:16: error: cannot bind non-const lvalue reference of type 'long long unsigned int&' to a value of type 'char'
   20 | #define b begin()
      |           ~~~~~^~
a.cc:106:17: note: in expansion of macro 'b'
  106 |         cin>>a>>b;
      |                 ^
/usr/include/c++/14/istream:219:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(float&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  219 |       operator>>(float& __f)
      |       ^~~~~~~~
/usr/include/c++/14/istream:219:7: note:   conversion of argument 1 would be ill-formed:
a.cc:20:16: error: cannot bind non-const lvalue reference of type 'float&' to a value of type 'char'
   20 | #define b begin()
      |           ~~~~~^~
a.cc:106:17: note: in expansion of macro 'b'
  106 |         cin>>a>>b;
      |                 ^
/usr/include/c++/14/istream:223:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(double&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  223 |       operator>>(double& __f)
      |       ^~~~~~~~
/usr/include/c++/14/istream:223:7: note:   conversion of argument 1 would be ill-formed:
a.cc:20:16: error: cannot bind non-const lvalue reference of type 'double&' to a value of type 'char'
   20 | #define b begin()
      |           ~~~~~^~
a.cc:106:17: note: in expansion of macro 'b'
  106 |         cin>>a>>b;
      |                 ^
/usr/include/c++/14/istream:227:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long double&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  227 |       operator>>(long double& __f)
      |       ^~~~~~~~
/usr/include/c++/14/istream:227:7: note:   conversion of argument 1 would be ill-formed:
a.cc:20:16: error: cannot bind non-const lvalue reference of type 'long double&' to a value of type 'char'
   20 | #define b begin()
      |           ~~~~~^~
a.cc:106:17: note: in expansion of macro 'b'
  106 |         cin>>a>>b;
      |                 ^
/usr/include/c++/14/istream:328:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(void*&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  328 |       operator>>(void*& __p)
      |       ^~~~~~~~
/usr/include/c++/14/istream:328:7: note:   conversion of argument 1 would be ill-formed:
a.cc:20:16: error: invalid conversion from 'char' to 'void*' [-fpermissive]
   20 | #define b begin()
      |           ~~~~~^~
      |                |
      |                char
a.cc:106:17: note: in expansion of macro 'b'
  106 |         cin>>a>>b;
      |                 ^
a.cc:20:16: error: cannot bind rvalue '(void*)((long int)begin())' to 'void*&'
   20 | #define b begin()
      |           ~~~~~^~
a.cc:106:17: note: in expansion of macro 'b'
  106