T = int(input())
for _ in range(T):
    N = int(input())
    S = list(input())
    stack = ["$", "$"]
    S.reverse()
    for s in S:
        if s == "B":
            stack.append(s)
        else:
            if stack[-1] == stack[-2] == "B":
                stack.pop()
            else:
                stack.append(s)
    stack.reverse()
    stack.pop()
    stack.pop()
    print("".join(stack))