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)