T=int(input())
for _ in range(T):
    N=int(input())
    A=list(map(list,input().split()))
    for i in range(N):
        while len(A[i])>1 and A[i][-1]=="0":
            A[i].pop()
        A[i]="".join(A[i])
    k=0
    v=0
    for a in A[1:]:
        if len(a)>k:
            k=len(a)
            v=a
    mn=int(v[-1])
    x=1
    while (mn*x)%10!=0:
        x+=1
    x*=10**(k-1)
    print(x)