Language: C++

#include <iostream>

using namespace std;

int main () {
    int m = -1, cur = 0, n;
    char c;
    cin >> n;
    for (register int i = 0; i < n; i++) {
        if(cur>m) {
            m = cur;
        }
        cin >> c;
        if(c=='I') {
            cur++;
        }
        else
            cur--;
    }
    cout << cur>m?cur:m << endl;
    return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:9:23: warning: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
    9 |     for (register int i = 0; i < n; i++) {
      |                       ^
a.cc:20:16: error: no match for 'operator>' (operand types are 'std::basic_ostream<char>' and 'int')
   20 |     cout << cur>m?cur:m << endl;
      |     ~~~~~~~~~~~^~
      |          |      |
      |          |      int
      |          std::basic_ostream<char>
a.cc:20:16: note: candidate: 'operator>(int, int)' (built-in)
   20 |     cout << cur>m?cur:m << endl;
      |     ~~~~~~~~~~~^~
a.cc:20:16: note:   no known conversion for argument 1 from 'std::basic_ostream<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:20:17: note:   'std::basic_ostream<char>' is not derived from 'const std::reverse_iterator<_Iterator>'
   20 |     cout << cur>m?cur:m << endl;
      |                 ^
/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:20:17: note:   'std::basic_ostream<char>' is not derived from 'const std::reverse_iterator<_Iterator>'
   20 |     cout << cur>m?cur:m << endl;
      |                 ^
/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:20:17: note:   'std::basic_ostream<char>' is not derived from 'const std::move_iterator<_IteratorL>'
   20 |     cout << cur>m?cur:m << endl;
      |                 ^
/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:20:17: note:   'std::basic_ostream<char>' is not derived from 'const std::move_iterator<_IteratorL>'
   20 |     cout << cur>m?cur:m << endl;
      |                 ^
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:20:17: note:   'std::basic_ostream<char>' is not derived from 'const std::pair<_T1, _T2>'
   20 |     cout << cur>m?cur:m << endl;
      |                 ^
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:20:17: note:   'std::basic_ostream<char>' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   20 |     cout << cur>m?cur:m << endl;
      |                 ^
/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:20:17: note:   'std::basic_ostream<char>' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   20 |     cout << cur>m?cur:m << endl;
      |                 ^
/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:20:17: note:   mismatched types 'std::basic_string_view<_CharT, _Traits>' and 'int'
   20 |     cout << cur>m?cur:m << endl;
      |                 ^
/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:20:17: note:   'std::basic_ostream<char>' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   20 |     cout << cur>m?cur:m << endl;
      |                 ^
/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:20:17: note:   'std::basic_ostream<char>' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   20 |     cout << cur>m?cur:m << endl;
      |                 ^
/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:20:17: note:   mismatched types 'const _CharT*' and 'std::basic_ostream<char>'
   20 |     cout << cur>m?cur:m << endl;
      |                 ^
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:20:17: note:   'std::basic_ostream<char>' is not derived from 'const std::tuple<_UTypes ...>'
   20 |     cout << cur>m?cur:m << endl;
      |                 ^
a.cc:20:25: error: invalid operands of types 'int' and '<unresolved overloaded function type>' to binary 'operator<<'
   20 |     cout << cur>m?cur:m << endl;
      |                       ~~^~~~~~~