from sys import stdin
input = stdin.readline

for _ in range(int(input())):
    L, R = map(int, input().split())

    if R == 0:
        print(0)
    elif L.bit_length() < R.bit_length():
        b = 1<<(R.bit_length()-1)
        a = b-1
        print(a*b)
    else:
        print(-1)