#include <algorithm>
#include <cmath>
#include <complex>
#include <iostream>
#include <map>
#include <queue>
#include <set>
#include <vector>

using namespace std;

using ll = long long;
using P = pair<int, int>;

const long long MOD = 1e9+7;

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }

int divide[100000];
vector<int> sieve(int n) {
    for (int i = 0; i < n + 1; i++) divide[i] = 1;
    vector<int> is_prime(n + 1, true);
    for (int i = 2; i <= n; i++) {
        if (!is_prime.at(i)) continue;
        
        is_prime.at(i) = true;
        divide[i] = i;
        for (int j = i + i; j <= n; j += i) {
            is_prime.at(j) = false;
            divide[j] = i;
        }
    }
    vector<int> res;
    for (int i = 2; i <= n; i++) if (is_prime.at(i)) res.push_back(i);
    return res;
}

map<int, int> prime_factor(int n) {
    map<int, int> res;
    while (1 < n) {
        res[divide[n]]++;
        n /= divide[n];
    }
    return res;
}

int main() {
    int n, k;
    cin >> n >> k;
    sieve(n);
    
    int max_div = 0;
    int ans = -1;
    auto nps = prime_factor(n);
    for (int i = 1; i < n; i++) {
        auto ps = prime_factor(i);
        int common_prime = 0;
        for (auto np: nps) common_prime += min(ps[np.first], np.second);
        //cout << i << " " << common_prime << endl;
        if (common_prime < k) continue;

        int d = 1;
        for (auto p: ps) d *= (p.second + 1);
        if (max_div < d) {
            max_div = d;
            ans = i;
        }
    }
    cout << ans << endl;
}