t = int(input())
for _ in range(t):
    n = int(input())
    s = input()
    st = []
    for c in s:
        if c == 'B':
            while len(st) >= 2 and st[-1] == 'B' and st[-2] == 'A':
                st.pop()
                st.pop()
        st.append(c)
    print(*st, sep='')