Language: C++

#include<bits/stdc++.h>
int main(){
  int x,n;
  cin >> x >> n;
  vector<int> a(n);
  for(int i=0;i<n;i++){
    cin >> a[i];
  }
  sort(a,a+n);
  reverse(a,a+n);
  cout << lower_bound(a,a+n,x)-a << endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:4:3: error: 'cin' was not declared in this scope; did you mean 'std::cin'?
    4 |   cin >> x >> n;
      |   ^~~
      |   std::cin
In file included from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:146,
                 from a.cc:1:
/usr/include/c++/14/iostream:62:18: note: 'std::cin' declared here
   62 |   extern istream cin;           ///< Linked to standard input
      |                  ^~~
a.cc:5:3: error: 'vector' was not declared in this scope
    5 |   vector<int> a(n);
      |   ^~~~~~
a.cc:5:3: note: suggested alternatives:
In file included from /usr/include/c++/14/vector:66,
                 from /usr/include/c++/14/functional:64,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:53:
/usr/include/c++/14/bits/stl_vector.h:428:11: note:   'std::vector'
  428 |     class vector : protected _Vector_base<_Tp, _Alloc>
      |           ^~~~~~
/usr/include/c++/14/vector:93:13: note:   'std::pmr::vector'
   93 |       using vector = std::vector<_Tp, polymorphic_allocator<_Tp>>;
      |             ^~~~~~
a.cc:5:10: error: expected primary-expression before 'int'
    5 |   vector<int> a(n);
      |          ^~~
a.cc:7:12: error: 'a' was not declared in this scope
    7 |     cin >> a[i];
      |            ^
a.cc:9:8: error: 'a' was not declared in this scope
    9 |   sort(a,a+n);
      |        ^
a.cc:9:3: error: 'sort' was not declared in this scope; did you mean 'std::sort'?
    9 |   sort(a,a+n);
      |   ^~~~
      |   std::sort
In file included from /usr/include/c++/14/algorithm:86,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51:
/usr/include/c++/14/pstl/glue_algorithm_defs.h:296:1: note: 'std::sort' declared here
  296 | sort(_ExecutionPolicy&& __exec, _RandomAccessIterator __first, _RandomAccessIterator __last);
      | ^~~~
a.cc:10:3: error: 'reverse' was not declared in this scope; did you mean 'std::reverse'?
   10 |   reverse(a,a+n);
      |   ^~~~~~~
      |   std::reverse
/usr/include/c++/14/pstl/glue_algorithm_defs.h:249:1: note: 'std::reverse' declared here
  249 | reverse(_ExecutionPolicy&& __exec, _BidirectionalIterator __first, _BidirectionalIterator __last);
      | ^~~~~~~
a.cc:11:3: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   11 |   cout << lower_bound(a,a+n,x)-a << endl;
      |   ^~~~
      |   std::cout
/usr/include/c++/14/iostream:63:18: note: 'std::cout' declared here
   63 |   extern ostream cout;          ///< Linked to standard output
      |                  ^~~~
a.cc:11:11: error: 'lower_bound' was not declared in this scope; did you mean 'std::lower_bound'?
   11 |   cout << lower_bound(a,a+n,x)-a << endl;
      |           ^~~~~~~~~~~
      |           std::lower_bound
In file included from /usr/include/c++/14/algorithm:61:
/usr/include/c++/14/bits/stl_algo.h:1963:5: note: 'std::lower_bound' declared here
 1963 |     lower_bound(_ForwardIterator __first, _ForwardIterator __last,
      |     ^~~~~~~~~~~
a.cc:11:37: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   11 |   cout << lower_bound(a,a+n,x)-a << endl;
      |                                     ^~~~
      |                                     std::endl
In file included from /usr/include/c++/14/istream:41,
                 from /usr/include/c++/14/sstream:40,
                 from /usr/include/c++/14/complex:45,
                 from /usr/include/c++/14/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:127:
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~