代码如下

#include<iostream>

#include<string>

#include<algorithm>

using namespace std;

int main(){

	string s;
  
	cin >> s;
  
	for(int i = 0 ;i < s.length(); ++i){
  
		if(s[i]+3 > 'Z'){
    
			s[i] = 'A'+(s[i]+3-'Z');
      
		}
    
		else if(s[i]+3 > 'z'){
    
			s[i] = 'a'+(s[i]+3-'z');
      
		}
    
		else s[i] += 3;
    
	}
  
	reverse(s.begin(), s.end());
  
	for(int i = 0; i < s.length(); ++i){
  
		if(s[i] >= 'a' && s[i] <= 'z'){
    
			s[i] -= 32;
      
		}
    
		else if(s[i] >= 'A' && s[i] <= 'Z'){
    
			s[i] += 32;
      
		} 
    
	} 
  
	cout << s;
  
	return 0;
  
}