Language: C++

#include <iostream>
#include <stack>
#include <string>
using namespace std;
int main()
{
	stack<string> blocks;
	string cmd,color;
	std::cin >> cmd;
	while(cmd != "quit")
	{
		if(cmd == "push")
		{
			cin >> color;
			blocks.push(color);
		}
		else if(cmd == "pop")
		{
			cout << blocks.top() >> endl;
			blocks.pop();
		}
		std::cin >> cmd;
	}
	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:19:46: error: no match for 'operator>>' (operand types are 'std::basic_ostream<char>' and '<unresolved overloaded function type>')
   19 |                         cout << blocks.top() >> endl;
      |                         ~~~~~~~~~~~~~~~~~~~~~^~~~~~~
In file included from /usr/include/c++/14/string:55,
                 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/basic_string.tcc:835:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::basic_istream<_CharT, _Traits>& std::operator>>(basic_istream<_CharT, _Traits>&, __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
  835 |     operator>>(basic_istream<_CharT, _Traits>& __in,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.tcc:835:5: note:   template argument deduction/substitution failed:
a.cc:19:49: note:   'std::basic_ostream<char>' is not derived from 'std::basic_istream<_CharT, _Traits>'
   19 |                         cout << blocks.top() >> endl;
      |                                                 ^~~~
In file included from /usr/include/c++/14/bits/memory_resource.h:38,
                 from /usr/include/c++/14/string:68:
/usr/include/c++/14/cstddef:131:5: note: candidate: 'template<class _IntegerType> constexpr std::__byte_op_t<_IntegerType> std::operator>>(byte, _IntegerType)'
  131 |     operator>>(byte __b, _IntegerType __shift) noexcept
      |     ^~~~~~~~
/usr/include/c++/14/cstddef:131:5: note:   template argument deduction/substitution failed:
a.cc:19:49: note:   couldn't deduce template parameter '_IntegerType'
   19 |                         cout << blocks.top() >> endl;
      |                                                 ^~~~
In file included from /usr/include/c++/14/istream:1109,
                 from /usr/include/c++/14/iostream:42:
/usr/include/c++/14/bits/istream.tcc:978:5: note: candidate: 'template<class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(basic_istream<_CharT, _Traits>&, _CharT&)'
  978 |     operator>>(basic_istream<_CharT, _Traits>& __in, _CharT& __c)
      |     ^~~~~~~~
/usr/include/c++/14/bits/istream.tcc:978:5: note:   template argument deduction/substitution failed:
a.cc:19:49: note:   'std::basic_ostream<char>' is not derived from 'std::basic_istream<_CharT, _Traits>'
   19 |                         cout << blocks.top() >> endl;
      |                                                 ^~~~
/usr/include/c++/14/istream:849:5: note: candidate: 'template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(basic_istream<char, _Traits>&, unsigned char&)'
  849 |     operator>>(basic_istream<char, _Traits>& __in, unsigned char& __c)
      |     ^~~~~~~~
/usr/include/c++/14/istream:849:5: note:   template argument deduction/substitution failed:
a.cc:19:49: note:   'std::basic_ostream<char>' is not derived from 'std::basic_istream<char, _Traits>'
   19 |                         cout << blocks.top() >> endl;
      |                                                 ^~~~
/usr/include/c++/14/istream:854:5: note: candidate: 'template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(basic_istream<char, _Traits>&, signed char&)'
  854 |     operator>>(basic_istream<char, _Traits>& __in, signed char& __c)
      |     ^~~~~~~~
/usr/include/c++/14/istream:854:5: note:   template argument deduction/substitution failed:
a.cc:19:49: note:   'std::basic_ostream<char>' is not derived from 'std::basic_istream<char, _Traits>'
   19 |                         cout << blocks.top() >> endl;
      |                                                 ^~~~
/usr/include/c++/14/istream:896:5: note: candidate: 'template<class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(basic_istream<_CharT, _Traits>&, _CharT*)'
  896 |     operator>>(basic_istream<_CharT, _Traits>& __in, _CharT* __s)
      |     ^~~~~~~~
/usr/include/c++/14/istream:896:5: note:   template argument deduction/substitution failed:
a.cc:19:49: note:   'std::basic_ostream<char>' is not derived from 'std::basic_istream<_CharT, _Traits>'
   19 |                         cout << blocks.top() >> endl;
      |                                                 ^~~~
/usr/include/c++/14/istream:939:5: note: candidate: 'template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(basic_istream<char, _Traits>&, unsigned char*)'
  939 |     operator>>(basic_istream<char, _Traits>& __in, unsigned char* __s)
      |     ^~~~~~~~
/usr/include/c++/14/istream:939:5: note:   template argument deduction/substitution failed:
a.cc:19:49: note:   'std::basic_ostream<char>' is not derived from 'std::basic_istream<char, _Traits>'
   19 |                         cout << blocks.top() >> endl;
      |                                                 ^~~~
/usr/include/c++/14/istream:945:5: note: candidate: 'template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(basic_istream<char, _Traits>&, signed char*)'
  945 |     operator>>(basic_istream<char, _Traits>& __in, signed char* __s)
      |     ^~~~~~~~
/usr/include/c++/14/istream:945:5: note:   template argument deduction/substitution failed:
a.cc:19:49: note:   'std::basic_ostream<char>' is not derived from 'std::basic_istream<char, _Traits>'
   19 |                         cout << blocks.top() >> endl;
      |                                                 ^~~~
/usr/include/c++/14/istream:1099:5: note: candidate: 'template<class _Istream, class _Tp> _Istream&& std::operator>>(_Istream&&, _Tp&&)'
 1099 |     operator>>(_Istream&& __is, _Tp&& __x)
      |     ^~~~~~~~
/usr/include/c++/14/istream:1099:5: note:   template argument deduction/substitution failed:
a.cc:19:49: note:   couldn't deduce template parameter '_Tp'
   19 |                         cout << blocks.top() >> endl;
      |                                                 ^~~~