import math as mt
t=int(input())
for _ in range(t):
	n,m=map(int,input().split())
	a=min(n,m)
	b=int(mt.sqrt(a))
	ok=False
	for i in range(2,b+1,1):
		if(n%i==0 and m%i==0):
			print(i)
			ok=True
			continue
	if(ok):
		continue
	if(max(n,m)%a==0 and a!=1):
		print(a)
		continue
	print(-1)