Language: C++

#include <iostream>
#include <deque>
#include <string>
#include <algorithm>
#include <cstdio>
#include <cstdlib>
using namespace std;

int main(){
	deque<int> a;
	int num, n;
	string command;

	cin>>n;
	for(int i=0;i<n;i++){
		cin>>command;
		if((command.length() >= 6) && (command[6] == 'F')){
			a.pop_front();
		}else if((command.length() >= 6) && (command[6] == 'L')){
			a.pop_back();
		}else if(command[0] == 'i'){
			cin>>num;
			a.push_front(num);
		}else if(command == "delete"){
			cin>>num;
			deque<long>::iterator iter;
			iter = find(a.begin(), a.end(), num);
			if(iter != a.end())
				a.erase(iter);
		}
	}

	
	for(int i=0;i<a.size();i++){
		if(i != 0) cout<<" ";
		cout<<a[i];
	}
	cout<<endl;
	
	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:27:60: error: no match for 'operator=' (operand types are 'std::deque<long int>::iterator' {aka 'std::_Deque_base<long int, std::allocator<long int> >::iterator'} and 'std::_Deque_iterator<int, int&, int*>')
   27 |                         iter = find(a.begin(), a.end(), num);
      |                                                            ^
In file included from /usr/include/c++/14/deque:66,
                 from a.cc:2:
/usr/include/c++/14/bits/stl_deque.h:172:24: note: candidate: 'constexpr std::_Deque_iterator<_Tp, _Ref, _Ptr>& std::_Deque_iterator<_Tp, _Ref, _Ptr>::operator=(const std::_Deque_iterator<_Tp, _Ref, _Ptr>&) [with _Tp = long int; _Ref = long int&; _Ptr = long int*]'
  172 |       _Deque_iterator& operator=(const _Deque_iterator&) = default;
      |                        ^~~~~~~~
/usr/include/c++/14/bits/stl_deque.h:172:34: note:   no known conversion for argument 1 from 'std::_Deque_iterator<int, int&, int*>' to 'const std::_Deque_iterator<long int, long int&, long int*>&'
  172 |       _Deque_iterator& operator=(const _Deque_iterator&) = default;
      |                                  ^~~~~~~~~~~~~~~~~~~~~~
a.cc:28:33: error: no match for 'operator!=' (operand types are 'std::deque<long int>::iterator' {aka 'std::_Deque_base<long int, std::allocator<long int> >::iterator'} and 'std::deque<int>::iterator' {aka 'std::_Deque_base<int, std::allocator<int> >::iterator'})
   28 |                         if(iter != a.end())
      |                            ~~~~ ^~ ~~~~~~~
      |                            |            |
      |                            |            _Deque_iterator<int,int&,int*>
      |                            _Deque_iterator<long int,long int&,long int*>
In file included from /usr/include/c++/14/iosfwd:42,
                 from /usr/include/c++/14/ios:40,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:1:
/usr/include/c++/14/bits/postypes.h:197:5: note: candidate: 'template<class _StateT> bool std::operator!=(const fpos<_StateT>&, const fpos<_StateT>&)'
  197 |     operator!=(const fpos<_StateT>& __lhs, const fpos<_StateT>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/postypes.h:197:5: note:   template argument deduction/substitution failed:
a.cc:28:42: note:   'std::deque<long int>::iterator' {aka 'std::_Deque_base<long int, std::allocator<long int> >::iterator'} is not derived from 'const std::fpos<_StateT>'
   28 |                         if(iter != a.end())
      |                                          ^
In file included from /usr/include/c++/14/string:43,
                 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:
/usr/include/c++/14/bits/allocator.h:243:5: note: candidate: 'template<class _T1, class _T2> bool std::operator!=(const allocator<_CharT>&, const allocator<_T2>&)'
  243 |     operator!=(const allocator<_T1>&, const allocator<_T2>&)
      |     ^~~~~~~~
/usr/include/c++/14/bits/allocator.h:243:5: note:   template argument deduction/substitution failed:
a.cc:28:42: note:   'std::deque<long int>::iterator' {aka 'std::_Deque_base<long int, std::allocator<long int> >::iterator'} is not derived from 'const std::allocator<_CharT>'
   28 |                         if(iter != a.end())
      |                                          ^
In file included from /usr/include/c++/14/string:48:
/usr/include/c++/14/bits/stl_iterator.h:455:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator!=(const reverse_iterator<_Iterator>&, const reverse_iterator<_Iterator>&)'
  455 |     operator!=(const reverse_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:455:5: note:   template argument deduction/substitution failed:
a.cc:28:42: note:   'std::deque<long int>::iterator' {aka 'std::_Deque_base<long int, std::allocator<long int> >::iterator'} is not derived from 'const std::reverse_iterator<_Iterator>'
   28 |                         if(iter != a.end())
      |                                          ^
/usr/include/c++/14/bits/stl_iterator.h:500:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator!=(const reverse_iterator<_Iterator>&, const reverse_iterator<_IteratorR>&)'
  500 |     operator!=(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:500:5: note:   template argument deduction/substitution failed:
a.cc:28:42: note:   'std::deque<long int>::iterator' {aka 'std::_Deque_base<long int, std::allocator<long int> >::iterator'} is not derived from 'const std::reverse_iterator<_Iterator>'
   28 |                         if(iter != a.end())
      |                                          ^
/usr/include/c++/14/bits/stl_iterator.h:1686:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator!=(const move_iterator<_IteratorL>&, const move_iterator<_IteratorR>&)'
 1686 |     operator!=(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1686:5: note:   template argument deduction/substitution failed:
a.cc:28:42: note:   'std::deque<long int>::iterator' {aka 'std::_Deque_base<long int, std::allocator<long int> >::iterator'} is not derived from 'const std::move_iterator<_IteratorL>'
   28 |                         if(iter != a.end())
      |                                          ^
/usr/include/c++/14/bits/stl_iterator.h:1753:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator!=(const move_iterator<_IteratorL>&, const move_iterator<_IteratorL>&)'
 1753 |     operator!=(const move_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1753:5: note:   template argument deduction/substitution failed:
a.cc:28:42: note:   'std::deque<long int>::iterator' {aka 'std::_Deque_base<long int, std::allocator<long int> >::iterator'} is not derived from 'const std::move_iterator<_IteratorL>'
   28 |                         if(iter != a.end())
      |                                          ^
In file included from /usr/include/c++/14/bits/stl_algobase.h:64,
                 from /usr/include/c++/14/string:51:
/usr/include/c++/14/bits/stl_pair.h:1052:5: note: candidate: 'template<class _T1, class _T2> constexpr bool std::operator!=(const pair<_T1, _T2>&, const pair<_T1, _T2>&)'
 1052 |     operator!=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:1052:5: note:   template argument deduction/substitution failed:
a.cc:28:42: note:   'std::deque<long int>::iterator' {aka 'std::_Deque_base<long int, std::allocator<long int> >::iterator'} is not derived from 'const std::pair<_T1, _T2>'
   28 |                         if(iter != a.end())
      |                                          ^
In file included from /usr/include/c++/14/bits/basic_string.h:47,
                 from /usr/include/c++/14/string:54:
/usr/include/c++/14/string_view:651:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator!=(basic_string_view<_CharT, _Traits>, basic_string_view<_CharT, _Traits>)'
  651 |     operator!=(basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:651:5: note:   template argument deduction/substitution failed:
a.cc:28:42: note:   'std::_Deque_iterator<long int, long int&, long int*>' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   28 |                         if(iter != a.end())
      |                                          ^
/usr/include/c++/14/string_view:658:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator!=(basic_string_view<_CharT, _Traits>, __type_identity_t<basic_string_view<_CharT, _Traits> >)'
  658 |     operator!=(basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:658:5: note:   template argument deduction/substitution failed:
a.cc:28:42: note:   'std::_Deque_iterator<long int, long int&, long int*>' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   28 |                         if(iter != a.end())
      |                                          ^
/usr/include/c++/14/string_view:666:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator!=(__type_identity_t<basic_string_view<_CharT, _Traits> >, basic_string_view<_CharT, _Traits>)'
  666 |     operator!=(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:666:5: note:   template argument deduction/substitution failed:
a.cc:28:42: note:   'std::_Deque_iterator<int, int&, int*>' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   28 |                         if(iter != a.end())
      |                                          ^
/usr/include/c++/14/bits/basic_string.h:3833:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator!=(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3833 |     operator!=(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3833:5: note:   template argument deduction/substitution failed:
a.cc:28:42: note:   'std::deque<long int>::iterator' {aka 'std::_Deque_base<long int, std::allocator<long int> >::iterator'} is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   28 |                         if(iter != a.end())
      |                                          ^
/usr/include/c++/14/bits/basic_string.h:3847:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator!=(const _CharT*, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3847 |     operator!=(const _CharT* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3847:5: note:   template argument deduction/substitution failed:
a.cc:28:42: note:   mismatched type