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

void solve() {
    int N;
    string S;
    cin >> N >> S;

    for (int i = 0; i < N; i++) {
        if (i % 2 == 0) {
            if (S[i] == 'C') {
                S[i] = 'A';
            } else {
                break;
            }
        } else {
            if (S[i] == 'A') {
                S[i] = 'B';
                break;
            } else if (S[i] == 'B') {
                S[i] = 'C';
            } else {
                break;
            }
        }
    }
    cout << S << "\n";
}

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    int T;
    cin >> T;

    while (T--) solve();
}