Language: C++

#include <iostream>
using namespace std;

int i, j, k;
char string[1500];

int main(void) {
	i = 0;
	cin >> string;
	while (string[i] != 0x00) {
		if (string[i] >= 'a' && string[i] <= 'z') {
			string[i] = string[i] - 32;
		} else if (string[i] >= 'A' && string[i] <= 'Z') {
			string[i] = string[i] + 32;
		}
		i++;
	}
	cout << string;
	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:9:16: error: reference to 'string' is ambiguous
    9 |         cin >> string;
      |                ^~~~~~
In file included from /usr/include/c++/14/iosfwd:41,
                 from /usr/include/c++/14/ios:40,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:1:
/usr/include/c++/14/bits/stringfwd.h:77:33: note: candidates are: 'typedef class std::__cxx11::basic_string<char> std::string'
   77 |   typedef basic_string<char>    string;
      |                                 ^~~~~~
a.cc:5:6: note:                 'char string [1500]'
    5 | char string[1500];
      |      ^~~~~~
a.cc:10:16: error: reference to 'string' is ambiguous
   10 |         while (string[i] != 0x00) {
      |                ^~~~~~
/usr/include/c++/14/bits/stringfwd.h:77:33: note: candidates are: 'typedef class std::__cxx11::basic_string<char> std::string'
   77 |   typedef basic_string<char>    string;
      |                                 ^~~~~~
a.cc:5:6: note:                 'char string [1500]'
    5 | char string[1500];
      |      ^~~~~~
a.cc:11:21: error: reference to 'string' is ambiguous
   11 |                 if (string[i] >= 'a' && string[i] <= 'z') {
      |                     ^~~~~~
/usr/include/c++/14/bits/stringfwd.h:77:33: note: candidates are: 'typedef class std::__cxx11::basic_string<char> std::string'
   77 |   typedef basic_string<char>    string;
      |                                 ^~~~~~
a.cc:5:6: note:                 'char string [1500]'
    5 | char string[1500];
      |      ^~~~~~
a.cc:11:41: error: reference to 'string' is ambiguous
   11 |                 if (string[i] >= 'a' && string[i] <= 'z') {
      |                                         ^~~~~~
/usr/include/c++/14/bits/stringfwd.h:77:33: note: candidates are: 'typedef class std::__cxx11::basic_string<char> std::string'
   77 |   typedef basic_string<char>    string;
      |                                 ^~~~~~
a.cc:5:6: note:                 'char string [1500]'
    5 | char string[1500];
      |      ^~~~~~
a.cc:12:25: error: reference to 'string' is ambiguous
   12 |                         string[i] = string[i] - 32;
      |                         ^~~~~~
/usr/include/c++/14/bits/stringfwd.h:77:33: note: candidates are: 'typedef class std::__cxx11::basic_string<char> std::string'
   77 |   typedef basic_string<char>    string;
      |                                 ^~~~~~
a.cc:5:6: note:                 'char string [1500]'
    5 | char string[1500];
      |      ^~~~~~
a.cc:12:37: error: reference to 'string' is ambiguous
   12 |                         string[i] = string[i] - 32;
      |                                     ^~~~~~
/usr/include/c++/14/bits/stringfwd.h:77:33: note: candidates are: 'typedef class std::__cxx11::basic_string<char> std::string'
   77 |   typedef basic_string<char>    string;
      |                                 ^~~~~~
a.cc:5:6: note:                 'char string [1500]'
    5 | char string[1500];
      |      ^~~~~~
a.cc:13:28: error: reference to 'string' is ambiguous
   13 |                 } else if (string[i] >= 'A' && string[i] <= 'Z') {
      |                            ^~~~~~
/usr/include/c++/14/bits/stringfwd.h:77:33: note: candidates are: 'typedef class std::__cxx11::basic_string<char> std::string'
   77 |   typedef basic_string<char>    string;
      |                                 ^~~~~~
a.cc:5:6: note:                 'char string [1500]'
    5 | char string[1500];
      |      ^~~~~~
a.cc:13:48: error: reference to 'string' is ambiguous
   13 |                 } else if (string[i] >= 'A' && string[i] <= 'Z') {
      |                                                ^~~~~~
/usr/include/c++/14/bits/stringfwd.h:77:33: note: candidates are: 'typedef class std::__cxx11::basic_string<char> std::string'
   77 |   typedef basic_string<char>    string;
      |                                 ^~~~~~
a.cc:5:6: note:                 'char string [1500]'
    5 | char string[1500];
      |      ^~~~~~
a.cc:14:25: error: reference to 'string' is ambiguous
   14 |                         string[i] = string[i] + 32;
      |                         ^~~~~~
/usr/include/c++/14/bits/stringfwd.h:77:33: note: candidates are: 'typedef class std::__cxx11::basic_string<char> std::string'
   77 |   typedef basic_string<char>    string;
      |                                 ^~~~~~
a.cc:5:6: note:                 'char string [1500]'
    5 | char string[1500];
      |      ^~~~~~
a.cc:14:37: error: reference to 'string' is ambiguous
   14 |                         string[i] = string[i] + 32;
      |                                     ^~~~~~
/usr/include/c++/14/bits/stringfwd.h:77:33: note: candidates are: 'typedef class std::__cxx11::basic_string<char> std::string'
   77 |   typedef basic_string<char>    string;
      |                                 ^~~~~~
a.cc:5:6: note:                 'char string [1500]'
    5 | char string[1500];
      |      ^~~~~~
a.cc:18:17: error: reference to 'string' is ambiguous
   18 |         cout << string;
      |                 ^~~~~~
/usr/include/c++/14/bits/stringfwd.h:77:33: note: candidates are: 'typedef class std::__cxx11::basic_string<char> std::string'
   77 |   typedef basic_string<char>    string;
      |                                 ^~~~~~
a.cc:5:6: note:                 'char string [1500]'
    5 | char string[1500];
      |      ^~~~~~