Language: C++

#include <iostream>
#include <vector>
using namespace std;

int main(){
  int n;
  cin > n;
  int cnt=0;
  vector<int> v(n);
  for (int i=0; i < n ; i++){
    cin >> v.at(i);
  }
  for (int j=1; j < n-1; j++){
    int pre=v.at(i-1);
    int now=v.at(i);
    int next=v.at(i+1);
    if ((pre < now && now < next) ||(next < now && now < pre)) cnt++;
  }
  cout << cnt << endl;
  return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:7:7: error: no match for 'operator>' (operand types are 'std::istream' {aka 'std::basic_istream<char>'} and 'int')
    7 |   cin > n;
      |   ~~~ ^ ~
      |   |     |
      |   |     int
      |   std::istream {aka std::basic_istream<char>}
a.cc:7:7: note: candidate: 'operator>(int, int)' (built-in)
    7 |   cin > n;
      |   ~~~~^~~
a.cc:7:7: note:   no known conversion for argument 1 from 'std::istream' {aka 'std::basic_istream<char>'} to 'int'
In file included from /usr/include/c++/14/string:48,
                 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/stl_iterator.h:462:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator>(const reverse_iterator<_Iterator>&, const reverse_iterator<_Iterator>&)'
  462 |     operator>(const reverse_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:462:5: note:   template argument deduction/substitution failed:
a.cc:7:9: note:   'std::istream' {aka 'std::basic_istream<char>'} is not derived from 'const std::reverse_iterator<_Iterator>'
    7 |   cin > n;
      |         ^
/usr/include/c++/14/bits/stl_iterator.h:507:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator>(const reverse_iterator<_Iterator>&, const reverse_iterator<_IteratorR>&)'
  507 |     operator>(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:507:5: note:   template argument deduction/substitution failed:
a.cc:7:9: note:   'std::istream' {aka 'std::basic_istream<char>'} is not derived from 'const std::reverse_iterator<_Iterator>'
    7 |   cin > n;
      |         ^
/usr/include/c++/14/bits/stl_iterator.h:1714:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator>(const move_iterator<_IteratorL>&, const move_iterator<_IteratorR>&)'
 1714 |     operator>(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1714:5: note:   template argument deduction/substitution failed:
a.cc:7:9: note:   'std::istream' {aka 'std::basic_istream<char>'} is not derived from 'const std::move_iterator<_IteratorL>'
    7 |   cin > n;
      |         ^
/usr/include/c++/14/bits/stl_iterator.h:1774:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator>(const move_iterator<_IteratorL>&, const move_iterator<_IteratorL>&)'
 1774 |     operator>(const move_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1774:5: note:   template argument deduction/substitution failed:
a.cc:7:9: note:   'std::istream' {aka 'std::basic_istream<char>'} is not derived from 'const std::move_iterator<_IteratorL>'
    7 |   cin > n;
      |         ^
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:1058:5: note: candidate: 'template<class _T1, class _T2> constexpr bool std::operator>(const pair<_T1, _T2>&, const pair<_T1, _T2>&)'
 1058 |     operator>(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:1058:5: note:   template argument deduction/substitution failed:
a.cc:7:9: note:   'std::istream' {aka 'std::basic_istream<char>'} is not derived from 'const std::pair<_T1, _T2>'
    7 |   cin > n;
      |         ^
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:695:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator>(basic_string_view<_CharT, _Traits>, basic_string_view<_CharT, _Traits>)'
  695 |     operator> (basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:695:5: note:   template argument deduction/substitution failed:
a.cc:7:9: note:   'std::basic_istream<char>' is not derived from 'std::basic_string_view<_CharT, _Traits>'
    7 |   cin > n;
      |         ^
/usr/include/c++/14/string_view:702:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator>(basic_string_view<_CharT, _Traits>, __type_identity_t<basic_string_view<_CharT, _Traits> >)'
  702 |     operator> (basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:702:5: note:   template argument deduction/substitution failed:
a.cc:7:9: note:   'std::basic_istream<char>' is not derived from 'std::basic_string_view<_CharT, _Traits>'
    7 |   cin > n;
      |         ^
/usr/include/c++/14/string_view:710:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator>(__type_identity_t<basic_string_view<_CharT, _Traits> >, basic_string_view<_CharT, _Traits>)'
  710 |     operator> (__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:710:5: note:   template argument deduction/substitution failed:
a.cc:7:9: note:   mismatched types 'std::basic_string_view<_CharT, _Traits>' and 'int'
    7 |   cin > n;
      |         ^
/usr/include/c++/14/bits/basic_string.h:3915:5: 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>&)'
 3915 |     operator>(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3915:5: note:   template argument deduction/substitution failed:
a.cc:7:9: note:   'std::istream' {aka 'std::basic_istream<char>'} is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
    7 |   cin > n;
      |         ^
/usr/include/c++/14/bits/basic_string.h:3929:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator>(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, const _CharT*)'
 3929 |     operator>(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3929:5: note:   template argument deduction/substitution failed:
a.cc:7:9: note:   'std::istream' {aka 'std::basic_istream<char>'} is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
    7 |   cin > n;
      |         ^
/usr/include/c++/14/bits/basic_string.h:3942:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator>(const _CharT*, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3942 |     operator>(const _CharT* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3942:5: note:   template argument deduction/substitution failed:
a.cc:7:9: note:   mismatched types 'const _CharT*' and 'std::basic_istream<char>'
    7 |   cin > n;
      |         ^
In file included from /usr/include/c++/14/bits/memory_resource.h:47,
                 from /usr/include/c++/14/string:68:
/usr/include/c++/14/tuple:2619:5: note: candidate: 'template<class ... _TElements, class ... _UElements> constexpr bool std::operator>(const tuple<_UTypes ...>&, const tuple<_Elements ...>&)'
 2619 |     operator>(const tuple<_TElements...>& __t,
      |     ^~~~~~~~
/usr/include/c++/14/tuple:2619:5: note:   template argument deduction/substitution failed:
a.cc:7:9: note:   'std::istream' {aka 'std::basic_istream<char>'} is not derived from 'const std::tuple<_UTypes ...>'
    7 |   cin > n;
      |         ^
In file included from /usr/include/c++/14/vector:66,
                 from a.cc:2:
/usr/include/c++/14/bits/stl_vector.h:2102:5: note: candidate: 'template<class _Tp, class _Alloc> bool std::operator>(const vector<_Tp, _Alloc>&, const vector<_Tp, _Alloc>&)'
 2102 |     operator>(const vector<_Tp, _Alloc>& __x, const vector<_Tp, _Alloc>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_vector.h:2102:5: note:   template argument deduction/substitution failed:
a.cc:7:9: note:   'std::istream' {aka 'std::basic_istream<char>'} is not derived from 'const std::vector<_Tp, _Alloc>'
    7 |   cin > n;
      |         ^
a.cc:14:18: error: 'i' was not declared in this scope
   14 |     int pre=v.at(i-1);
      |                  ^