import sys

# sys.setrecursionlimit(200005)
# sys.set_int_max_str_digits(200005)
int1 = lambda x: int(x)-1
pDB = lambda *x: print(*x, end="\n", file=sys.stderr)
p2D = lambda x: print(*x, sep="\n", end="\n\n", file=sys.stderr)
def II(): return int(sys.stdin.readline())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def LI1(): return list(map(int1, sys.stdin.readline().split()))
def LLI1(rows_number): return [LI1() for _ in range(rows_number)]
def SI(): return sys.stdin.readline().rstrip()

dij = [(0, 1), (-1, 0), (0, -1), (1, 0)]
# dij = [(0, 1), (-1, 0), (0, -1), (1, 0), (1, 1), (1, -1), (-1, 1), (-1, -1)]
# inf = -1-(-1 << 31)
inf = -1-(-1 << 62)

# md = 10**9+7
md = 998244353

class Sieve:
    def __init__(self, n):
        self.plist = [2]
        min_prime_factor = [2, 0]*(n//2+1)
        for x in range(3, n+1, 2):
            if min_prime_factor[x] == 0:
                min_prime_factor[x] = x
                self.plist.append(x)
                if x**2 > n: continue
                for y in range(x**2, n+1, 2*x):
                    if min_prime_factor[y] == 0:
                        min_prime_factor[y] = x
        self.min_prime_factor = min_prime_factor

    def isprime(self, x):
        return self.min_prime_factor[x] == x

    def pf(self, x):
        pp, ee = [], []
        while x > 1:
            mpf = self.min_prime_factor[x]
            if pp and mpf == pp[-1]:
                ee[-1] += 1
            else:
                pp.append(mpf)
                ee.append(1)
            x //= mpf
        return pp, ee

    # unsorted
    def factor(self, a):
        ff = [1]
        pp, ee = self.pf(a)
        for p, e in zip(pp, ee):
            ff, gg = [], ff
            w = p
            for _ in range(e):
                for f in gg: ff.append(f*w)
                w *= p
            ff += gg
        return ff

from random import randrange

def is_prime(n):
    # K...信頼度
    K = 10
    if n == 2: return True
    if n == 1 or n & 1 == 0: return False
    d = (n-1) >> 1
    while d & 1 == 0: d >>= 1
    for k in range(K):
        a = randrange(1, n)
        t = d
        y = pow(a, t, n)
        while t != n-1 and y != 1 and y != n-1:
            y = pow(y, 2, n)
            t <<= 1
        if y != n-1 and t & 1 == 0: return False
    return True

from bisect import bisect

sv=Sieve(22248596)
pp=sv.plist[1:]
l,r=LI()
for i in range(1,len(pp)):
    b=pp[i]
    if 9*b>r:
        print(-1)
        exit()
    for j in range(i):
        a=pp[j]
        ab=a*a*b
        if ab*pp[-1]<l:
            c=(l+ab-1)//ab
            while c<=r and not is_prime(c):c+=1
            if c<=r:
                print(ab*c)
                exit()
        else:
            k=bisect(pp,r//(a*a*b))-1
            if k<=i:break
            if ab*pp[k]>=l:
                print(ab*pp[k])
                exit()
print(-1)