#include <bits/stdc++.h>
using namespace std;
int main () {
	int T;
	cin >> T;
	while (T--) {
		int N;
		string s;
		cin >> N >> s;
		for (int i = 0; i < N; i ++) {
			if (i & 1) {
				if (s[i] == 'C') break;
				else s[i] ++;
			} else {
				if (s[i] != 'C') break;
				else s[i] = 'A';
			}
		}
		cout << s << endl;
	}
}