#define _USE_MATH_DEFINES
#include <cstdio>
#include <iostream>
#include <sstream>
#include <fstream>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <complex>
#include <string>
#include <vector>
#include <array>
#include <list>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <bitset>
#include <numeric>
#include <limits>
#include <climits>
#include <cfloat>
#include <functional>
#include <iterator>
#include <memory>
#include <regex>
using namespace std;

int gcd(int a, int b){
    while(b != 0){
        int tmp = a % b;
        a = b;
        b = tmp;
    }
    return a;
}

void integerFactorization(int n, vector<pair<int, int> >& factor)
{
    factor.clear();
    int a = 2;
    while(a * a <= n){
        int b = 0;
        while(n % a == 0){
            ++ b;
            n /= a;
        }
        if(b > 0)
            factor.push_back(make_pair(a, b));
        ++ a;
    }
    if(n > 1)
        factor.push_back(make_pair(n, 1));
}

int solve(int x, int n, int k)
{
    int y = gcd(x, n);
    vector<pair<int, int> > f;
    integerFactorization(y, f);

    for(const auto& p : f)
        k -= p.second;
    if(k > 0)
        return -1;
    
    integerFactorization(x, f);
    int ans = 1;
    for(const auto& p : f)
        ans *= p.second + 1;
    return ans;
}

int main()
{
    int n, k;
    cin >> n >> k;

    int maxCnt = -1;
    int ans = -1;
    for(int x=1; x<n; ++x){
        int cnt = solve(x, n, k);
        if(maxCnt < cnt){
            maxCnt = cnt;
            ans = x;
        }
    }
    cout << ans << endl;

    return 0;
}