N,K = map(int,input().split())
P = list(range(N+1))
for i in range(2,N+1):
    if i*i>N:break
    for j in range(i*i,N+1,i):
        P[j] = P[i]
C = {}
x = N
while x>1:
    C[P[x]] = C.get(P[x],0)+1
    x = x//P[x]
ans = 0
nmax = 0
for a in range(2,N):
    D = {}
    x = a
    while x>1:
        D[P[x]] = D.get(P[x],0)+1
        x = x//P[x]
    tot = 0
    num = 1
    for p in D:
        if p in C:
            tot += min(D[p],C[p])
        num *= D[p]+1
    if tot>=K and num>nmax:
        ans = a
        nmax = num
print(ans)