#include <bits/stdc++.h>
using namespace std;

int main() {
    int N, K;
    cin >> N >> K;
    vector<int> fact(N);
    vector<int> num(N, 1);
    for (int i = 1; i < N; i++) {
        for (int j = 1; i * j <= N; j++) {
            fact[i]++;
        }
    }
    num[1] = 0;
    for (int i = 2; i * i < N; i++) {
        if (num[i] != 1) continue;
        for (int j = 2; i * j < N; j++) num[i * j] = num[i] + num[j];
    }
    int max = 0, res = 0;
    for (int i = 1; i < N; i++) {
        if (num[__gcd(i, N)] >= K && fact[i] > max)
            res = i, max = fact[i];
    }
    cout << res << endl;
}