Language: C++

#include<bits/stdc++.h>

#define REP(i,s,n) for(int (i)=s; (i)<(int)(n);(i)++)
#define RIT(it,c) for(__typeof(c.begin()) it = c.begin();it!=c.end();it++)
#define ALL(x) x.begin(), x.end()
#define SZ(x) (int)(x).size()
#define MSET(m,v) memset(m,v,sizeof(m))


using namespace std;


typedef long long LL;
typedef vector<int> vi;
typedef pair<int,int> ii;
typedef pair<int,ii> iii;
typedef vector<LL> vL;
typedef vector<bool> vb;
typedef pair<int,vi> iv;
typedef pair<LL,LL> pLL; 
typedef long double LD;


int main(){
	int N;
	cin>>N;
	map<int,vi> cnt;
	for(int i=1;i<=N;++i){
		int A;
		cin>>A;
		cnt[-A].push_back(i);
	}
	vi v;
	for(auto p:cnt){
		if(p.second>=2) v.push_back(-p.first);
		if(v.size()>=2){
			cout<< (LL)v[0]*v[1]<<endl;
			return 0;
		}
		if(p.second>=4){
			cout<<(LL)p.second*p.second<<endl;
			return 0;
		}
	}
	cout<<0<<endl;
	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:35:28: error: no match for 'operator>=' (operand types are 'std::vector<int>' and 'int')
   35 |                 if(p.second>=2) v.push_back(-p.first);
      |                    ~~~~~~~~^~~
      |                      |       |
      |                      |       int
      |                      std::vector<int>
In file included from /usr/include/c++/14/regex:68,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:181,
                 from a.cc:1:
/usr/include/c++/14/bits/regex.h:1165:5: note: candidate: 'template<class _BiIter> bool std::__cxx11::operator>=(const sub_match<_BiIter>&, const sub_match<_BiIter>&)'
 1165 |     operator>=(const sub_match<_BiIter>& __lhs, const sub_match<_BiIter>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1165:5: note:   template argument deduction/substitution failed:
a.cc:35:30: note:   'std::vector<int>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   35 |                 if(p.second>=2) v.push_back(-p.first);
      |                              ^
/usr/include/c++/14/bits/regex.h:1248:5: note: candidate: 'template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::__cxx11::operator>=(__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&, const sub_match<_BiIter>&)'
 1248 |     operator>=(const __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1248:5: note:   template argument deduction/substitution failed:
a.cc:35:30: note:   'std::vector<int>' is not derived from 'std::__cxx11::__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>'
   35 |                 if(p.second>=2) v.push_back(-p.first);
      |                              ^
/usr/include/c++/14/bits/regex.h:1341:5: note: candidate: 'template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::__cxx11::operator>=(const sub_match<_BiIter>&, __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&)'
 1341 |     operator>=(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1341:5: note:   template argument deduction/substitution failed:
a.cc:35:30: note:   'std::vector<int>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   35 |                 if(p.second>=2) v.push_back(-p.first);
      |                              ^
/usr/include/c++/14/bits/regex.h:1415:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator>=(const typename std::iterator_traits<_Iter>::value_type*, const sub_match<_BiIter>&)'
 1415 |     operator>=(typename iterator_traits<_Bi_iter>::value_type const* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1415:5: note:   template argument deduction/substitution failed:
a.cc:35:30: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'int'
   35 |                 if(p.second>=2) v.push_back(-p.first);
      |                              ^
/usr/include/c++/14/bits/regex.h:1509:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator>=(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type*)'
 1509 |     operator>=(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1509:5: note:   template argument deduction/substitution failed:
a.cc:35:30: note:   'std::vector<int>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   35 |                 if(p.second>=2) v.push_back(-p.first);
      |                              ^
/usr/include/c++/14/bits/regex.h:1586:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator>=(const typename std::iterator_traits<_Iter>::value_type&, const sub_match<_BiIter>&)'
 1586 |     operator>=(typename iterator_traits<_Bi_iter>::value_type const& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1586:5: note:   template argument deduction/substitution failed:
a.cc:35:30: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'int'
   35 |                 if(p.second>=2) v.push_back(-p.first);
      |                              ^
/usr/include/c++/14/bits/regex.h:1686:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator>=(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type&)'
 1686 |     operator>=(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1686:5: note:   template argument deduction/substitution failed:
a.cc:35:30: note:   'std::vector<int>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   35 |                 if(p.second>=2) v.push_back(-p.first);
      |                              ^
In file included from /usr/include/c++/14/bits/stl_algobase.h:64,
                 from /usr/include/c++/14/algorithm:60,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51:
/usr/include/c++/14/bits/stl_pair.h:1070:5: note: candidate: 'template<class _T1, class _T2> constexpr bool std::operator>=(const pair<_T1, _T2>&, const pair<_T1, _T2>&)'
 1070 |     operator>=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:1070:5: note:   template argument deduction/substitution failed:
a.cc:35:30: note:   'std::vector<int>' is not derived from 'const std::pair<_T1, _T2>'
   35 |                 if(p.second>=2) v.push_back(-p.first);
      |                              ^
In file included from /usr/include/c++/14/bits/stl_algobase.h:67:
/usr/include/c++/14/bits/stl_iterator.h:476:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator>=(const reverse_iterator<_Iterator>&, const reverse_iterator<_Iterator>&)'
  476 |     operator>=(const reverse_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:476:5: note:   template argument deduction/substitution failed:
a.cc:35:30: note:   'std::vector<int>' is not derived from 'const std::reverse_iterator<_Iterator>'
   35 |                 if(p.second>=2) v.push_back(-p.first);
      |                              ^
/usr/include/c++/14/bits/stl_iterator.h:520:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator>=(const reverse_iterator<_Iterator>&, const reverse_iterator<_IteratorR>&)'
  520 |     operator>=(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:520:5: note:   template argument deduction/substitution failed:
a.cc:35:30: note:   'std::vector<int>' is not derived from 'const std::reverse_iterator<_Iterator>'
   35 |                 if(p.second>=2) v.push_back(-p.first);
      |                              ^
/usr/include/c++/14/bits/stl_iterator.h:1724:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator>=(const move_iterator<_IteratorL>&, const move_iterator<_IteratorR>&)'
 1724 |     operator>=(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1724:5: note:   template argument deduction/substitution failed:
a.cc:35:30: note:   'std::vector<int>' is not derived from 'const std::move_iterator<_IteratorL>'
   35 |                 if(p.second>=2) v.push_back(-p.first);
      |                              ^
/usr/include/c++/14/bits/stl_iterator.h:1781:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator>=(const move_iterator<_IteratorL>&, const move_iterator<_IteratorL>&)'
 1781 |     operator>=(const move_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1781:5: note:   template argument deduction/substitution failed:
a.cc:35:30: note:   'std::vector<int>' is not derived from 'const std::move_iterator<_IteratorL>'
   35 |                 if(p.second>=2) v.push_back(-p.first);
      |                              ^
In file included from /usr/include/c++/14/bits/basic_string.h:47,
                 from /usr/include/c++/14/string:54,
                 from /usr/include/c++/14/bitset:52,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:52:
/usr/include/c++/14/string_view:739:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator>=(basic_string_view<_CharT, _Traits>, basic_string_view<_CharT, _Traits>)'
  739 |     operator>=(basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:739:5: note:   template argument deduction/substitution failed:
a.cc:35:30: note:   'std::vector<int>' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   35 |                 if(p.second>=2) v.push_back(-p.first);
      |                              ^
/usr/include/c++/14/string_view:746:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator>=(basic_string_view<_CharT, _Traits>, __type_identity_t<basic_string_view<_CharT, _Traits> >)'
  746 |     operator>=(basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:746:5: note:   template argument deduction/substitution failed:
a.cc:35:30: note:   'std::vector<int>' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   35 |                 if(p.second>=2) v.push_back(-p.first);
      |                              ^
/usr/include/c++/14/string_view:754:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator>=(__type_identity_t<basic_string_view<_CharT, _Traits> >, basic_string_view<_CharT, _Traits>)'
  754 |     operator>=(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:754:5: note:   template argument deduction/substitution failed:
a.cc:35:30: note:   mismatched types 'std::basic_string_view<_CharT, _Traits>' and 'int'
   35 |                 if(p.second>=2) v.push_back(-p.first);
      |                              ^
/usr/include/c++/14/bits/basic_string.h:3997:5: 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>&)'
 3997 |     operator>=(const basic_string<_