C++ :

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;
const int N = 10010;
char ch[N];
int main()
{
    string s;
    getline(cin , s);

    for (int i = 0; i < s.size(); ++i) {
        if(s[i] >= 'a' && s[i] <= 'z'){
            s[i] = s[i] + 3;//向右移动三位恢复原文的位置
            if(s[i] > 'z') s[i] = s[i] - 26;//如果过原来移动的是x,y,z改为a,b,c
            s[i] = s[i] - 32;//将小写改成大写
        }else if(s[i] >= 'A' && s[i] <= 'Z'){
            s[i] = s[i] + 3;//向右移动三个位置
            if(s[i] > 'Z') s[i] = s[i] - 26;//若是X,Y,Z就改为A,B,C
            s[i] = s[i] + 32;//将大写改成小写
        }
    }
    for (int j = s.size() - 1; j >= 0 ; --j) cout << s[j];
    return 0;
}