So easy!

#include <bits/stdc++.h>
using namespace std;
int main()
{
    string s;
    getline(cin,s);
    for (int i = s.size() - 1;i >= 0;i--)
    {
        if (s[i] >= 'A' && s[i] <= 'Z') cout << s[i];
    }
    for (int i = 0;i < s.size();i++)
    {
        if (s[i] >= 'a' && s[i] <= 'z') cout << s[i];
    }
}