def primeset(N): #N以下の素数をsetで求める.エラトステネスの篩O(√Nlog(N))
    lsx = [1]*(N+1)
    for i in range(2,int(-(-N**0.5//1))+1):
        if lsx[i] == 1:
            for j in range(i,N//i+1):
                lsx[j*i] = 0
    setprime = set()
    for i in range(2,N+1):
        if lsx[i] == 1:
            setprime.add(i)
    return setprime

def factorization_all_n(n):#n以下の自然数すべてをを素因数分解
    lspn = [[] for i in range(n+1)]
    lsnum = [i for i in range(n+1)]
    lsp = list(primeset(n))
    lsp.sort()
    for p in lsp:
        for j in range(1,n//p+1):
            cnt = 0
            while lsnum[p*j]%p==0:
                lsnum[p*j] //= p
                cnt += 1
            lspn[j*p].append((p,cnt))
    return lspn

import collections
N,K = map(int,input().split())
lspn = factorization_all_n(N+1)
np = collections.Counter()
for i,j in lspn[N]:
    np[i] = j
yaku = 0
for i in range(2,N):
    k = 0
    for j,k1 in lspn[i]:
        k += min(np[j],k1)
    if K > k:
        continue
    y = 1
    for j,k in lspn[i]:
        y *= k+1
    if yaku < y:
        ans = i
        yaku = y
print(ans)