import math
MAX_PRIME = 100000+10
isPrime = [1 for i in range(MAX_PRIME)]
primes = []
isPrime[0] = 0
isPrime[1] = 0
for i in range(2, MAX_PRIME) :
    if isPrime[i] == 1:
        for j in range(i + i, MAX_PRIME, i) :
            isPrime[j] = 0
        primes.append(i)
L, H = list(map(int, input().split()))
minPrimes = -1
ans = -1
SZ = len(primes)
for i in range(SZ) :
    for j in range(i+1) :
        k = primes[i] * primes[j]
        if L <= k <= H :
            tmp = primes[j]
            if minPrimes < tmp :
                minPrimes = tmp
                ans = k
            elif minPrimes == tmp :
                ans = max(ans, k)
        elif k > H :
            break
print(ans)