N, K = map(int, input().split())

def gcd(x, y):
    while y:
        x, y = y, x % y
    return x

def divisor(n):
    res = set()
    i = 1
    while i * i <= n:
        if n % i == 0:
            res.add(i)
            res.add(n // i)
        i += 1
    return sorted(res)

def factorize(n):
    if n == 1: return []
    res = []
    x, y = n, 2
    while y * y <= x:
        while x % y == 0:
            res.append(y)
            x //= y
        y += 1
    if x > 1:
        res.append(x)
    return res

maxdiv = 0
res = 0

for i in range(1, N):
    g = gcd(N, i)
    if len(factorize(g)) >= K:
        d = len(divisor(i))
        if maxdiv < d:
            res = i
            maxdiv = d

print(res)