from math import gcd

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

# エラストネスの篩応用　素因数の数
P = [0] * (N + 1)
P[0] = 0
for i in range(2, N):
    if P[i] == 0:
        for j in range(i, N + 1, i):
            P[j] += 1
        tmp = i * i
        while tmp <= N:
            for j in range(tmp, N + 1, tmp):
                P[j] += 1
            tmp *= i

# エラストネスの篩応用　約数の数
Q = [2] * (N + 1)
Q[0] = 0
Q[1] = 0
for i in range(2, N):
    if i * i > N:
        break
    for j in range(2 * i, N + 1, i):
        if i * i > j:
            continue
        if i * i == j:
            Q[j] += 1
        else:
            Q[j] += 2

ndiv = 0
ans = 0
for i in range(1, N):
    if P[gcd(i, N)] >= K:
        if ndiv < Q[i]:
            ndiv = Q[i]
            ans = i
print(ans)