def find_abc(cs: list, used: set):
    a = b = c = INF
    for i, x in enumerate(cs):
        if x == 'A':
            if i not in used:
                a = min(a, i)
        elif x == 'B':
            if i not in used:
                b = min(b, i)
        elif x == 'C':
            if i not in used:
                c = min(c, i)

    return a, b, c


def f(cs: list, used: set):
    a, b, c = find_abc(cs, used)
    if c < a and c < b:
        cs[c] = 'A'
        used.add(c)
        return g(cs, used)

    return cs


def g(cs: list, used: set):
    a, b, c = find_abc(cs, used)
    if c < a and c < b:
        return cs

    if a < b:
        cs[a] = 'B'
        used.add(a)
    else:
        cs[b] = 'C'
        used.add(b)

    return f(cs, used)


def solve():
    N = int(input())
    S = input()
    res = f(list(S), set())
    return ''.join(res)


INF = 1 << 60
T = int(input())
for _ in range(T):
    ans = solve()
    print(ans)