t=int(input())
for _ in range(t):
    n=int(input())
    A=list(map(int,input().split()))
    X=[0]*(len(A)+3)
    for i in A:
        if i>=len(X):
            X[0]+=1
        else:
            X[i]+=1
    if n==1:
        print(A[0])
        continue
    def check(ans):
        if len(X)<=ans:
            return False
        d=0
        dov=0
        for i in range(ans,len(X)):
            dov+=X[i]
        for i in reversed(range(1,ans)):
            qq=X[i]-d
            if qq<=0:
                d+=1-qq
            else:
                dov+=qq-1
        
        return X[0]-d+dov>=1
                
                
    ans=0
    #print(X)
    for bs in reversed(range(20)):
        ans+=2**bs
        if not check(ans):
            ans-=2**bs
    print(ans)