#include <bits/stdc++.h>
// #include <atcoder/all>
using namespace std;
// using namespace atcoder;
#define rep(i, a, n) for(int i = a; i < n; i++)
#define rrep(i, a, n) for(int i = a; i >= n; i--)
#define inr(l, x, r) (l <= x && x < r)
#define ll long long
#define ld long double

// using mint = modint1000000007;
// using mint = modint998244353;
constexpr int IINF = 1001001001;
constexpr ll INF = 1e18;

template<class t,class u> void chmax(t&a,u b){if(a<b)a=b;}
template<class t,class u> void chmin(t&a,u b){if(b<a)a=b;}

int main(){
    int t; cin >> t;
    while(t--){
        int n; cin >> n;
        string s; cin >> s;
        bool f = false;
        rep(i, 0, n){
            if(i%2 == 0){
                if(f) break;
                else if(s[i] == 'C') s[i] -= 2;
                else break;
            }else{
                if(s[i] == 'A'){
                    s[i]++;
                    f = true;
                }else if(s[i] == 'B'){
                    s[i]++;
                }else break;
            }
        }
        cout << s << endl;
    }
    return 0;
}