Language: C++

#include <bits/stdlib.h>
using namespace std;

int main(){
  string s;
  cin >> s;
  int N = s.size();
  for(int i = 0;  i < N; i++){
    if(i%2 == 0){
      cout << s.at(i);
    }
  }
  cout << endl;
}
    

Compiler output:
In file included from a.cc:1:
/usr/include/x86_64-linux-gnu/bits/stdlib.h:20:3: error: #error "Never include <bits/stdlib.h> directly; use <stdlib.h> instead."
   20 | # error "Never include <bits/stdlib.h> directly; use <stdlib.h> instead."
      |   ^~~~~
/usr/include/x86_64-linux-gnu/bits/stdlib.h:25:30: error: 'size_t' has not been declared
   25 |                              size_t __resolvedlen) __THROW __wur;
      |                              ^~~~~~
/usr/include/x86_64-linux-gnu/bits/stdlib.h:25:52: error: expected initializer before '__THROW'
   25 |                              size_t __resolvedlen) __THROW __wur;
      |                                                    ^~~~~~~
/usr/include/x86_64-linux-gnu/bits/stdlib.h:26:30: error: '__realpath_alias' was not declared in this scope
   26 | extern char *__REDIRECT_NTH (__realpath_alias,
      |                              ^~~~~~~~~~~~~~~~
/usr/include/x86_64-linux-gnu/bits/stdlib.h:27:31: error: expected primary-expression before 'const'
   27 |                              (const char *__restrict __name,
      |                               ^~~~~
/usr/include/x86_64-linux-gnu/bits/stdlib.h:27:31: error: expected ')' before 'const'
   27 |                              (const char *__restrict __name,
      |                              ~^~~~~
      |                               )
/usr/include/x86_64-linux-gnu/bits/stdlib.h:29:14: error: redefinition of 'char* __REDIRECT_NTH'
   29 | extern char *__REDIRECT_NTH (__realpath_chk_warn,
      |              ^~~~~~~~~~~~~~
/usr/include/x86_64-linux-gnu/bits/stdlib.h:26:14: note: 'char* __REDIRECT_NTH' previously defined here
   26 | extern char *__REDIRECT_NTH (__realpath_alias,
      |              ^~~~~~~~~~~~~~
/usr/include/x86_64-linux-gnu/bits/stdlib.h:29:30: error: '__realpath_chk_warn' was not declared in this scope
   29 | extern char *__REDIRECT_NTH (__realpath_chk_warn,
      |                              ^~~~~~~~~~~~~~~~~~~
/usr/include/x86_64-linux-gnu/bits/stdlib.h:30:31: error: expected primary-expression before 'const'
   30 |                              (const char *__restrict __name,
      |                               ^~~~~
/usr/include/x86_64-linux-gnu/bits/stdlib.h:30:31: error: expected ')' before 'const'
   30 |                              (const char *__restrict __name,
      |                              ~^~~~~
      |                               )
/usr/include/x86_64-linux-gnu/bits/stdlib.h:36:1: error: '__fortify_function' does not name a type
   36 | __fortify_function __attribute_overloadable__ __wur char *
      | ^~~~~~~~~~~~~~~~~~
/usr/include/x86_64-linux-gnu/bits/stdlib.h:59:52: error: 'size_t' has not been declared
   59 | extern int __ptsname_r_chk (int __fd, char *__buf, size_t __buflen,
      |                                                    ^~~~~~
/usr/include/x86_64-linux-gnu/bits/stdlib.h:60:29: error: 'size_t' has not been declared
   60 |                             size_t __nreal) __THROW __nonnull ((2))
      |                             ^~~~~~
/usr/include/x86_64-linux-gnu/bits/stdlib.h:60:45: error: expected initializer before '__THROW'
   60 |                             size_t __nreal) __THROW __nonnull ((2))
      |                                             ^~~~~~~
/usr/include/x86_64-linux-gnu/bits/stdlib.h:62:12: error: conflicting declaration 'int __REDIRECT_NTH'
   62 | extern int __REDIRECT_NTH (__ptsname_r_alias, (int __fd, char *__buf,
      |            ^~~~~~~~~~~~~~
/usr/include/x86_64-linux-gnu/bits/stdlib.h:26:14: note: previous declaration as 'char* __REDIRECT_NTH'
   26 | extern char *__REDIRECT_NTH (__realpath_alias,
      |              ^~~~~~~~~~~~~~
/usr/include/x86_64-linux-gnu/bits/stdlib.h:62:28: error: '__ptsname_r_alias' was not declared in this scope
   62 | extern int __REDIRECT_NTH (__ptsname_r_alias, (int __fd, char *__buf,
      |                            ^~~~~~~~~~~~~~~~~
/usr/include/x86_64-linux-gnu/bits/stdlib.h:62:48: error: expected primary-expression before 'int'
   62 | extern int __REDIRECT_NTH (__ptsname_r_alias, (int __fd, char *__buf,
      |                                                ^~~
/usr/include/x86_64-linux-gnu/bits/stdlib.h:62:48: error: expected ')' before 'int'
   62 | extern int __REDIRECT_NTH (__ptsname_r_alias, (int __fd, char *__buf,
      |                                               ~^~~
      |                                                )
/usr/include/x86_64-linux-gnu/bits/stdlib.h:65:12: error: conflicting declaration 'int __REDIRECT_NTH'
   65 | extern int __REDIRECT_NTH (__ptsname_r_chk_warn,
      |            ^~~~~~~~~~~~~~
/usr/include/x86_64-linux-gnu/bits/stdlib.h:26:14: note: previous declaration as 'char* __REDIRECT_NTH'
   26 | extern char *__REDIRECT_NTH (__realpath_alias,
      |              ^~~~~~~~~~~~~~
/usr/include/x86_64-linux-gnu/bits/stdlib.h:65:28: error: '__ptsname_r_chk_warn' was not declared in this scope
   65 | extern int __REDIRECT_NTH (__ptsname_r_chk_warn,
      |                            ^~~~~~~~~~~~~~~~~~~~
/usr/include/x86_64-linux-gnu/bits/stdlib.h:66:29: error: expected primary-expression before 'int'
   66 |                            (int __fd, char *__buf, size_t __buflen,
      |                             ^~~
/usr/include/x86_64-linux-gnu/bits/stdlib.h:66:29: error: expected ')' before 'int'
   66 |                            (int __fd, char *__buf, size_t __buflen,
      |                            ~^~~
      |                             )
/usr/include/x86_64-linux-gnu/bits/stdlib.h:71:1: error: '__fortify_function' does not name a type
   71 | __fortify_function __attribute_overloadable__ int
      | ^~~~~~~~~~~~~~~~~~
/usr/include/x86_64-linux-gnu/bits/stdlib.h:85:54: error: 'size_t' has not been declared
   85 | extern int __wctomb_chk (char *__s, wchar_t __wchar, size_t __buflen)
      |                                                      ^~~~~~
/usr/include/x86_64-linux-gnu/bits/stdlib.h:86:3: error: expected initializer before '__THROW'
   86 |   __THROW __wur;
      |   ^~~~~~~
/usr/include/x86_64-linux-gnu/bits/stdlib.h:87:12: error: conflicting declaration 'int __REDIRECT_NTH'
   87 | extern int __REDIRECT_NTH (__wctomb_alias, (char *__s, wchar_t __wchar),
      |            ^~~~~~~~~~~~~~
/usr/include/x86_64-linux-gnu/bits/stdlib.h:26:14: note: previous declaration as 'char* __REDIRECT_NTH'
   26 | extern char *__REDIRECT_NTH (__realpath_alias,
      |              ^~~~~~~~~~~~~~
/usr/include/x86_64-linux-gnu/bits/stdlib.h:87:28: error: '__wctomb_alias' was not declared in this scope
   87 | extern int __REDIRECT_NTH (__wctomb_alias, (char *__s, wchar_t __wchar),
      |                            ^~~~~~~~~~~~~~
/usr/include/x86_64-linux-gnu/bits/stdlib.h:87:45: error: expected primary-expression before 'char'
   87 | extern int __REDIRECT_NTH (__wctomb_alias, (char *__s, wchar_t __wchar),
      |                                             ^~~~
/usr/include/x86_64-linux-gnu/bits/stdlib.h:87:45: error: expected ')' before 'char'
   87 | extern int __REDIRECT_NTH (__wctomb_alias, (char *__s, wchar_t __wchar),
      |                                            ~^~~~
      |                                             )
/usr/include/x86_64-linux-gnu/bits/stdlib.h:90:1: error: '__fortify_function' does not name a type
   90 | __fortify_function __attribute_overloadable__ __wur int
      | ^~~~~~~~~~~~~~~~~~
/usr/include/x86_64-linux-gnu/bits/stdlib.h:107:8: error: 'size_t' does not name a type
  107 | extern size_t __mbstowcs_chk (wchar_t *__restrict __dst,
      |        ^~~~~~
/usr/include/x86_64-linux-gnu/bits/stdlib.h:1:1: note: 'size_t' is defined in header '<cstddef>'; this is probably fixable by adding '#include <cstddef>'
  +++ |+#include <cstddef>
    1 | /* Checking macros for stdlib functions.
/usr/include/x86_64-linux-gnu/bits/stdlib.h:111:8: error: 'size_t' does not name a type
  111 | extern size_t __REDIRECT_NTH (__mbstowcs_nulldst,
      |        ^~~~~~
/usr/include/x86_64-linux-gnu/bits/stdlib.h:111:8: note: 'size_t' is defined in header '<cstddef>'; this is probably fixable by adding '#include <cstddef>'
/usr/include/x86_64-linux-gnu/bits/stdlib.h:116:8: error: 'size_t' does not name a type
  116 | extern size_t __REDIRECT_NTH (__mbstowcs_alias,
      |        ^~~~~~
/usr/include/x86_64-linux-gnu/bits/stdlib.h:116:8: note: 'size_t' is defined in header '<cstddef>'; this is probably fixable by adding '#include <cstddef>'
/usr/include/x86_64-linux-gnu/bits/stdlib.h:121:8: error: 'size_t' does not name a type
  121 | extern size_t __REDIRECT_NTH (__mbstowcs_chk_warn,
      |        ^~~~~~
/usr/include/x86_64-linux-gnu/bits/stdlib.h:121:8: note: 'size_t' is defined in header '<cstddef>'; this is probably fixable by adding '#include <cstddef>'
/usr/include/x86_64-linux-gnu/bits/stdlib.h:128:1: error: '__fortify_function' does not name a type
  128 | __fortify_function __attribute_overloadable__ size_t
      | ^~~~~~~~~~~~~~~~~~
/usr/include/x86_64-linux-gnu/bits/stdlib.h:143:8: error: 'size_t' does not name a type
  143 | extern size_t __wcstombs_chk (char *__restrict __dst,
      |        ^~~~~~
/usr/include/x86_64-linux-gnu/bits/stdlib.h:143:8: note: 'size_t' is defined in header '<cstddef>'; this is probably fixable by adding '#include <cstddef>'
/usr/include/x86_64-linux-gnu/bits/stdlib.h:147:8: error: 'size_t' does not name a type
  147 | extern size_t __REDIRECT_NTH (__wcstombs_alias,
      |        ^~~~~~
/usr/include/x86_64-linux-gnu/bits/stdlib.h:147:8: note: 'size_t' is defined in header '<cstddef>'; this is probably fixable by adding '#include <cstddef>'
/usr/include/x86_64-linux-gnu/bits/stdlib.h:152:8: error: 'size_t' does not name a type
  152 | extern size_t __REDIRECT_NTH (__wcstombs_chk_warn,
      |        ^~~~~~
/usr/include/x86_64-linux-gnu/bits/stdlib.h:152:8: note: 'size_t' is defined in header '<cstddef>'; this is probably fixable by adding '#include <cstddef>'
/usr/include/x86_64-linux-gnu/bits/stdlib.h:158:1: error: '__fortify_function' does not name a type
  158 | __fortify_function __attribute_overloadable__ size_t
      | ^~~~~~~~~~~~~~~~~~
a.cc: In function 'int main()':
a.cc:5:3: error: 'string' was not decl