import sys
input = sys.stdin.readline

T=int(input())
for t in range(T):
    N=int(input())
    S=input().strip()
    stack = []
    for s in S:
        if s=="B":
            while len(stack)>=2:
                if stack[-2]=="A" and stack[-1]=="B":
                    stack.pop()
                    stack.pop()
                else:break
        stack.append(s)
    print("".join(stack))