import sys

# sys.setrecursionlimit(200005)
int1 = lambda x: int(x)-1
p2D = lambda x: print(*x, sep="\n")
def II(): return int(sys.stdin.readline())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LI1(): return list(map(int1, sys.stdin.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
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 = 10**16
# md = 998244353
md = 10**9+7

l, h = LI()
lim = round(h**0.5)+3
pp = []
isp = [True]*lim
for p in range(2, lim):
    if isp[p]:
        pp.append(p)
        for c in range(p*p, lim, p):
            isp[c] = False
# print(pp)

fin = set()
ans = mx = -1
for p in pp[::-1]:
    if p < mx: break
    L = max(p,(l+p-1)//p)
    H = h//p+1
    for a in range(L, H):
        if a*p in fin:continue
        fin.add(a*p)
        for q in pp:
            if a*p%q == 0:
                if q == mx:
                    if a*p > ans:
                        ans = a*p
                if q > mx:
                    mx = q
                    ans = a*p
                break

print(ans)