Language: C++

#include <iostream>
#include <algorithm>
#include <vector>
#include <stack>
#include <queue>
#include <map>
#include <cmath>
#include <string>
#include <sstream>
#include <iomanip>
#include <complex>
using namespace std;

#define ll long long
#define vvi vector< vector<int> >
#define vi vector<int>
#define All(X) X.begin(),X.end()
#define FOR(i,a,b) for(int i=(int)(a);i<(int)(b);i++)
#define REP(i,n) for(int i=0;i<(int)(n);i++)
#define pb push_back
#define pii pair<int,int>
#define mp make_pair
ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}
ll lcm(ll a,ll b){return a/gcd(a,b)*b;}

int main(){
	string str;
	cin >> str;
	REP(i,str.size()){
		/*
		??¢???????????????'A'-'Z' < 'a' -'z'??¨????????? 'Z'??¨'a'?????????????¨?????????????
		http://www.asciitable.com/
		*/
		if('A'<=str[i]&&str[i]<='Z') cout << char (str+'a'-'A');
		else if('a'<=str[i]&&str[i]<='z') cout << char (str-('a'-'A')) << endl;
		else cout << str[i];
	}
}

Compiler output:
a.cc: In function 'int main()':
a.cc:34:67: error: no match for 'operator-' (operand types are 'std::__cxx11::basic_string<char>' and 'char')
   34 |                 if('A'<=str[i]&&str[i]<='Z') cout << char (str+'a'-'A');
      |                                                            ~~~~~~~^~~~
      |                                                               |    |
      |                                                               |    char
      |                                                               std::__cxx11::basic_string<char>
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:618:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr decltype ((__y.base() - __x.base())) std::operator-(const reverse_iterator<_Iterator>&, const reverse_iterator<_IteratorR>&)'
  618 |     operator-(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:618:5: note:   template argument deduction/substitution failed:
a.cc:34:68: note:   'std::__cxx11::basic_string<char>' is not derived from 'const std::reverse_iterator<_Iterator>'
   34 |                 if('A'<=str[i]&&str[i]<='Z') cout << char (str+'a'-'A');
      |                                                                    ^~~
/usr/include/c++/14/bits/stl_iterator.h:1790:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr decltype ((__x.base() - __y.base())) std::operator-(const move_iterator<_IteratorL>&, const move_iterator<_IteratorR>&)'
 1790 |     operator-(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1790:5: note:   template argument deduction/substitution failed:
a.cc:34:68: note:   'std::__cxx11::basic_string<char>' is not derived from 'const std::move_iterator<_IteratorL>'
   34 |                 if('A'<=str[i]&&str[i]<='Z') cout << char (str+'a'-'A');
      |                                                                    ^~~
In file included from a.cc:11:
/usr/include/c++/14/complex:370:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator-(const complex<_Tp>&, const complex<_Tp>&)'
  370 |     operator-(const complex<_Tp>& __x, const complex<_Tp>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/complex:370:5: note:   template argument deduction/substitution failed:
a.cc:34:68: note:   'std::__cxx11::basic_string<char>' is not derived from 'const std::complex<_Tp>'
   34 |                 if('A'<=str[i]&&str[i]<='Z') cout << char (str+'a'-'A');
      |                                                                    ^~~
/usr/include/c++/14/complex:379:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator-(const complex<_Tp>&, const _Tp&)'
  379 |     operator-(const complex<_Tp>& __x, const _Tp& __y)
      |     ^~~~~~~~
/usr/include/c++/14/complex:379:5: note:   template argument deduction/substitution failed:
a.cc:34:68: note:   'std::__cxx11::basic_string<char>' is not derived from 'const std::complex<_Tp>'
   34 |                 if('A'<=str[i]&&str[i]<='Z') cout << char (str+'a'-'A');
      |                                                                    ^~~
/usr/include/c++/14/complex:388:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator-(const _Tp&, const complex<_Tp>&)'
  388 |     operator-(const _Tp& __x, const complex<_Tp>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/complex:388:5: note:   template argument deduction/substitution failed:
a.cc:34:68: note:   mismatched types 'const std::complex<_Tp>' and 'char'
   34 |                 if('A'<=str[i]&&str[i]<='Z') cout << char (str+'a'-'A');
      |                                                                    ^~~
/usr/include/c++/14/complex:465:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator-(const complex<_Tp>&)'
  465 |     operator-(const complex<_Tp>& __x)
      |     ^~~~~~~~
/usr/include/c++/14/complex:465:5: note:   candidate expects 1 argument, 2 provided
a.cc:35:68: error: no match for 'operator-' (operand types are 'std::string' {aka 'std::__cxx11::basic_string<char>'} and 'int')
   35 |                 else if('a'<=str[i]&&str[i]<='z') cout << char (str-('a'-'A')) << endl;
      |                                                                 ~~~^~~~~~~~~~
      |                                                                 |       |
      |                                                                 |       int
      |                                                                 std::string {aka std::__cxx11::basic_string<char>}
/usr/include/c++/14/bits/stl_iterator.h:618:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr decltype ((__y.base() - __x.base())) std::operator-(const reverse_iterator<_Iterator>&, const reverse_iterator<_IteratorR>&)'
  618 |     operator-(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:618:5: note:   template argument deduction/substitution failed:
a.cc:35:77: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::reverse_iterator<_Iterator>'
   35 |                 else if('a'<=str[i]&&str[i]<='z') cout << char (str-('a'-'A')) << endl;
      |                                                                             ^
/usr/include/c++/14/bits/stl_iterator.h:1790:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr decltype ((__x.base() - __y.base())) std::operator-(const move_iterator<_IteratorL>&, const move_iterator<_IteratorR>&)'
 1790 |     operator-(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1790:5: note:   template argument deduction/substitution failed:
a.cc:35:77: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::move_iterator<_IteratorL>'
   35 |                 else if('a'<=str[i]&&str[i]<='z') cout << char (str-('a'-'A')) << endl;
      |                                                                             ^
/usr/include/c++/14/complex:370:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator-(const complex<_Tp>&, const complex<_Tp>&)'
  370 |     operator-(const complex<_Tp>& __x, const complex<_Tp>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/complex:370:5: note:   template argument deduction/substitution failed:
a.cc:35:77: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::complex<_Tp>'
   35 |                 else if('a'<=str[i]&&str[i]<='z') cout << char (str-('a'-'A')) << endl;
      |                                                                             ^
/usr/include/c++/14/complex:379:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator-(const complex<_Tp>&, const _Tp&)'
  379 |     operator-(const complex<_Tp>& __x, const _Tp& __y)
      |     ^~~~~~~~
/usr/include/c++/14/complex:379:5: note:   template argument deduction/substitution failed:
a.cc:35:77: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::complex<_Tp>'
   35 |                 else if('a'<=str[i]&&str[i]<='z') cout << char (str-('a'-'A')) << endl;
      |                                                                             ^
/usr/include/c++/14/complex:388:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator-(const _Tp&, const complex<_Tp>&)'
  388 |     operator-(const _Tp& __x, const complex<_Tp>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/complex:388:5: note:   template argument deduction/substitution failed:
a.cc:35:77: note:   mismatched types 'const std::complex<_Tp>' and 'int'
   35 |                 else if('a'<=str[i]&&str[i]<='z') cout << char (str-('a'-'A')) << endl;
      |                                                                             ^
/usr/include/c++/14/complex:465:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator-(const complex<_Tp>&)'
  465 |     operator-(const complex<_Tp>& __x)
      |     ^~~~~~~~
/usr/include/c++/14/complex:465:5: note:   candidate expects 1 argument, 2 provided