#include <iostream>
#include <vector>
#include <string>
 
using namespace std;
 
char shiftUp(char ch, int shift) {
    return 'a' + (ch - 'a' + shift) % 26;
}
 
char shiftDown(char ch, int shift) {
    return 'a' + (ch - 'a' - shift + 26) % 26;
}
 
void processTestCase(int n, const string& s, const string& q, string& result) {
    for (int i = 0; i < n; ++i) {
        int shift = i + 1;
        if (q[i] == 'U') {
            result[i] = shiftUp(s[i], shift);
        } else if (q[i] == 'D') {
            result[i] = shiftDown(s[i], shift);
        }
    }
}
 
int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
 
    int T;
    cin >> T;
 
    vector<string> results;
    results.reserve(T);
 
    for (int t = 0; t < T; ++t) {
        int n;
        cin >> n;
        string s, q;
        cin >> s >> q;
 
        string result(n, ' ');
        processTestCase(n, s, q, result);
        results.push_back(result);
    }
 
    for (const auto& result : results) {
        cout << result << endl;
    }
 
    return 0;
}