def sieve(n):
    primes = [1 if i%2 == 1 else 0 for i in range(n + 1)]
    primes[1] = 0
    primes[2] = 1
    for i in range(3,n + 1,2):
        if i * i > n:
            break
        if primes[i]:
            for j in range(i * i,n + 1,i):
                primes[j] = 0
    return [p for p in range(2,n + 1) if primes[p] == 1]

def Factor(n,k,primes,fact):
    ans = 1
    common_prime = 0
    for p in primes:
        cnt = 1
        while n%p == 0:
            n //= p
            cnt += 1
        ans *= cnt
        if p in fact:
            common_prime += min(cnt - 1,fact[p])
    if n!= 1:
        ans *= 2
        if n in fact:
            common_prime += 1
    if common_prime >= k:
        return ans
    else:
        return -1

n,k = map(int,input().split())
primes = sieve(int(n ** 0.5) + 3)
fact = {}
m = n
for p in primes:
    while n%p == 0:
        n //= p
        if p in fact:
            fact[p] += 1
        else:
            fact[p] = 1
if n != 1:
    fact[n] = 1

ans = 10 ** 9
cnt = 0
for i in range(1,m):
    ret = Factor(i,k,primes,fact)
    if cnt < ret:
        ans = i
        cnt = ret
print(ans)