有一个数值100%

#include<bits/stdc++.h>
using namespace std;

int main()
{
    string s = "abcdefghijklmnopqrstuvwxyz";
    string s2 = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    string a;
    cin>>a;
    for(int i = a.size()-1;i>=0;i--)
        {
            if(a[i]>='a')
                cout<<s2[(a[i]-'a'+3)%26];
            else
                cout<<s[(a[i]-'A'+3)%26];
        }
}