Language: C++

#include<iostream>
#include<algorithm>
#include<stdio.h>
#include<string>
#include<cmath>
#include<vector>
#include<queue>
#include<stack>
#include<functional>
#include<map>
using namespace std;
typedef long long ll;
int main()
{
	int n=0,x;
	int res=0;
	map a;
	cin>>n;
	for(int i=1;i<=n;i++)
	{
		cin>>x;
		if(a[x]==0){a[x]++;res++;}
	}
	cout<<res<<endl;
	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:17:13: error: class template argument deduction failed:
   17 |         map a;
      |             ^
a.cc:17:13: error: no matching function for call to 'map()'
In file included from /usr/include/c++/14/map:63,
                 from a.cc:10:
/usr/include/c++/14/bits/stl_map.h:302:9: note: candidate: 'template<class _Key, class _Tp, class _Compare, class _Alloc, class _InputIterator> map(_InputIterator, _InputIterator, const _Compare&, const _Alloc&)-> std::map<_Key, _Tp, _Compare, _Alloc>'
  302 |         map(_InputIterator __first, _InputIterator __last,
      |         ^~~
/usr/include/c++/14/bits/stl_map.h:302:9: note:   candidate expects 3 arguments, 0 provided
/usr/include/c++/14/bits/stl_map.h:285:9: note: candidate: 'template<class _Key, class _Tp, class _Compare, class _Alloc, class _InputIterator> map(_InputIterator, _InputIterator)-> std::map<_Key, _Tp, _Compare, _Alloc>'
  285 |         map(_InputIterator __first, _InputIterator __last)
      |         ^~~
/usr/include/c++/14/bits/stl_map.h:285:9: note:   candidate expects 2 arguments, 0 provided
/usr/include/c++/14/bits/stl_map.h:268:9: note: candidate: 'template<class _Key, class _Tp, class _Compare, class _Alloc, class _InputIterator> map(_InputIterator, _InputIterator, const _Alloc&)-> std::map<_Key, _Tp, _Compare, _Alloc>'
  268 |         map(_InputIterator __first, _InputIterator __last,
      |         ^~~
/usr/include/c++/14/bits/stl_map.h:268:9: note:   candidate expects 3 arguments, 0 provided
/usr/include/c++/14/bits/stl_map.h:262:7: note: candidate: 'template<class _Key, class _Tp, class _Compare, class _Alloc> map(std::initializer_list<std::pair<const _Key, _Val> >, const _Alloc&)-> std::map<_Key, _Tp, _Compare, _Alloc>'
  262 |       map(initializer_list<value_type> __l, const allocator_type& __a)
      |       ^~~
/usr/include/c++/14/bits/stl_map.h:262:7: note:   candidate expects 2 arguments, 0 provided
/usr/include/c++/14/bits/stl_map.h:256:7: note: candidate: 'template<class _Key, class _Tp, class _Compare, class _Alloc> map(std::map<_Key, _Tp, _Compare, _Allocator>&&, std::__type_identity_t<_Alloc>&)-> std::map<_Key, _Tp, _Compare, _Alloc>'
  256 |       map(map&& __m, const __type_identity_t<allocator_type>& __a)
      |       ^~~
/usr/include/c++/14/bits/stl_map.h:256:7: note:   candidate expects 2 arguments, 0 provided
/usr/include/c++/14/bits/stl_map.h:252:7: note: candidate: 'template<class _Key, class _Tp, class _Compare, class _Alloc> map(const std::map<_Key, _Tp, _Compare, _Allocator>&, std::__type_identity_t<_Alloc>&)-> std::map<_Key, _Tp, _Compare, _Alloc>'
  252 |       map(const map& __m, const __type_identity_t<allocator_type>& __a)
      |       ^~~
/usr/include/c++/14/bits/stl_map.h:252:7: note:   candidate expects 2 arguments, 0 provided
/usr/include/c++/14/bits/stl_map.h:248:7: note: candidate: 'template<class _Key, class _Tp, class _Compare, class _Alloc> map(const _Alloc&)-> std::map<_Key, _Tp, _Compare, _Alloc>'
  248 |       map(const allocator_type& __a)
      |       ^~~
/usr/include/c++/14/bits/stl_map.h:248:7: note:   candidate expects 1 argument, 0 provided
/usr/include/c++/14/bits/stl_map.h:240:7: note: candidate: 'template<class _Key, class _Tp, class _Compare, class _Alloc> map(std::initializer_list<std::pair<const _Key, _Val> >, const _Compare&, const _Alloc&)-> std::map<_Key, _Tp, _Compare, _Alloc>'
  240 |       map(initializer_list<value_type> __l,
      |       ^~~
/usr/include/c++/14/bits/stl_map.h:240:7: note:   candidate expects 1 argument, 0 provided
/usr/include/c++/14/bits/stl_map.h:227:7: note: candidate: 'template<class _Key, class _Tp, class _Compare, class _Alloc> map(std::map<_Key, _Tp, _Compare, _Allocator>&&)-> std::map<_Key, _Tp, _Compare, _Alloc>'
  227 |       map(map&&) = default;
      |       ^~~
/usr/include/c++/14/bits/stl_map.h:227:7: note:   candidate expects 1 argument, 0 provided
/usr/include/c++/14/bits/stl_map.h:219:7: note: candidate: 'template<class _Key, class _Tp, class _Compare, class _Alloc> map(const std::map<_Key, _Tp, _Compare, _Allocator>&)-> std::map<_Key, _Tp, _Compare, _Alloc>'
  219 |       map(const map&) = default;
      |       ^~~
/usr/include/c++/14/bits/stl_map.h:219:7: note:   candidate expects 1 argument, 0 provided
/usr/include/c++/14/bits/stl_map.h:206:7: note: candidate: 'template<class _Key, class _Tp, class _Compare, class _Alloc> map(const _Compare&, const _Alloc&)-> std::map<_Key, _Tp, _Compare, _Alloc>'
  206 |       map(const _Compare& __comp,
      |       ^~~
/usr/include/c++/14/bits/stl_map.h:206:7: note:   candidate expects 1 argument, 0 provided
/usr/include/c++/14/bits/stl_map.h:197:7: note: candidate: 'template<class _Key, class _Tp, class _Compare, class _Alloc> map()-> std::map<_Key, _Tp, _Compare, _Alloc>'
  197 |       map() = default;
      |       ^~~
/usr/include/c++/14/bits/stl_map.h:197:7: note:   template argument deduction/substitution failed:
a.cc:17:13: note:   couldn't deduce template parameter '_Key'
   17 |         map a;
      |             ^
/usr/include/c++/14/bits/stl_map.h:102:11: note: candidate: 'template<class _Key, class _Tp, class _Compare, class _Alloc> map(std::map<_Key, _Tp, _Compare, _Alloc>)-> std::map<_Key, _Tp, _Compare, _Alloc>'
  102 |     class map
      |           ^~~
/usr/include/c++/14/bits/stl_map.h:102:11: note:   candidate expects 1 argument, 0 provided
/usr/include/c++/14/bits/stl_map.h:1495:5: note: candidate: 'template<class _Key, class _Tp, class _Allocator, class> std::map(initializer_list<pair<_T1, _T2> >, _Allocator)-> map<_Key, _Tp, less<_Key>, _Allocator>'
 1495 |     map(initializer_list<pair<_Key, _Tp>>, _Allocator)
      |     ^~~
/usr/include/c++/14/bits/stl_map.h:1495:5: note:   candidate expects 2 arguments, 0 provided
/usr/include/c++/14/bits/stl_map.h:1489:5: note: candidate: 'template<class _InputIterator, class _Allocator, class, class> std::map(_InputIterator, _InputIterator, _Allocator)-> map<typename remove_const<typename iterator_traits< <template-parameter-1-1> >::value_type::first_type>::type, typename iterator_traits< <template-parameter-1-1> >::value_type::second_type, less<typename remove_const<typename iterator_traits< <template-parameter-1-1> >::value_type::first_type>::type>, _Allocator>'
 1489 |     map(_InputIterator, _InputIterator, _Allocator)
      |     ^~~
/usr/include/c++/14/bits/stl_map.h:1489:5: note:   candidate expects 3 arguments, 0 provided
/usr/include/c++/14/bits/stl_map.h:1482:5: note: candidate: 'template<class _Key, class _Tp, class _Compare, class _Allocator, class, class> std::map(initializer_list<pair<_T1, _T2> >, _Compare, _Allocator)-> map<_Key, _Tp, _Compare, _Allocator>'
 1482 |     map(initializer_list<pair<_Key, _Tp>>,
      |     ^~~
/usr/include/c++/14/bits/stl_map.h:1482:5: note:   candidate expects 1 argument, 0 provided
/usr/include/c++/14/bits/stl_map.h:1473:5: note: candidate: 'template<class _InputIterator, class _Compare, class _Allocator, class, class, class> std::map(_InputIterator, _InputIterator, _Compare, _Allocator)-> map<typename remove_const<typename iterator_traits< <template-parameter-1-1> >::value_type::first_type>::type, typename iterator_traits< <template-parameter-1-1> >::value_type::second_type, _Compare, _Allocator>'
 1473 |     map(_InputIterator, _InputIterator,
      |     ^~~
/usr/include/c++/14/bits/stl_map.h:1473:5: note:   candidate expects 2 arguments, 0 provided