for _ in range(int(input())):
    x, y = map(int, input().split())

    if x == 1 or y == 1 or x == 0 or y == 0:
        print("-1")
    else:
        
        lcd = min(x, y)

        
        for i in range(2, lcd + 1):
            if x % i == 0 and y % i == 0:
                lcd = i
                break

        print(lcd)