def solve():
    N = int(input())
    S = list(input())
    S.append("?")

    prev = [-1] * N
    stack = []
    for i in range(N):
        if S[i] == "A":
            stack.append(i)
        else:
            if stack:
                prev[i] = stack.pop()

    ans = [N]
    i = N - 1
    while i >= 0:
        if prev[i] == -1:
            ans.append(i)
            i -= 1
        else:
            if S[ans[-1]] != "B":
                ans.append(i)
                i -= 1
            else:
                i = prev[i] - 1

    ans.reverse()
    ans.pop()
    print("".join(S[i] for i in ans))


T = int(input())
for _ in range(T):
    solve()