import sys


def input(): return sys.stdin.readline().rstrip()


def isprime(x):
    i = 2
    while i*i <= x:
        if x % i == 0:
            return False
        i += 1
    return True


def main():
    t = int(input())
    for _ in range(t):
        n, k = map(int, input().split())
        for i in range(k+1, n+1):
            if isprime(i):
                print(i)
                break
        else:
            print(-1)


if __name__ == "__main__":
    main()