#include <iostream>
#include <algorithm>
#include <vector>
#include <string.h>
#include <cassert>
#include <queue>
using namespace std;
using lint = long long;
const lint mod = 1000000007;
#define all(x) (x).begin(), (x).end()
#define bitcount(n) __builtin_popcountl((lint)(n))
#define fcout cout << fixed << setprecision(15)
#define highest(x) (63 - __builtin_clzl(x))
template<class T> inline void YES(T condition){ if(condition) cout << "YES" << endl; else cout << "NO" << endl; }
template<class T> inline void Yes(T condition){ if(condition) cout << "Yes" << endl; else cout << "No" << endl; }
template<class T = string, class U = char>int character_count(T text, U character){ int ans = 0; for(U i: text){ ans += (i == character); } return ans; }
lint power(lint base, lint exponent, lint module){ if(exponent % 2){ return power(base, exponent - 1, module) * base % module; }else if(exponent){ lint root_ans = power(base, exponent / 2, module); return root_ans * root_ans % module; }else{ return 1; }}
struct position{ int y, x; }; position mv[4] = {{0, -1}, {1, 0}, {0, 1}, {-1, 0}};
template<class T, class U> string to_string(pair<T, U> x){ return to_string(x.first) + "," + to_string(x.second); } string to_string(string x){ return x; }
template<class itr> void array_output(itr start, itr goal){ string ans; for(auto i = start; i != goal; i++) ans += to_string(*i) + " "; if(!ans.empty()) ans.pop_back(); cout << ans << endl; }
template<class itr> void cins(itr first, itr last){ for(auto i = first; i != last; i++){ cin >> (*i); } }
template<class T> T gcd(T a, T b){ if(a && b){ return gcd(min(a, b), max(a, b) % min(a, b)); }else{ return a; }} template<class T> T lcm(T a, T b){ return a / gcd(a, b) * b; }
struct combination{ vector<lint> fact, inv; combination(int sz) : fact(sz + 1), inv(sz + 1){ fact[0] = 1; for(int i = 1; i <= sz; i++){ fact[i] = fact[i - 1] * i % mod; } inv[sz] = power(fact[sz], mod - 2, mod); for(int i = sz - 1; i >= 0; i--){ inv[i] = inv[i + 1] * (i + 1) % mod; } } lint C(int p, int q) const{ if(q < 0 || p < q) return 0; return (fact[p] * inv[q] % mod * inv[p - q] % mod); } };
template<class itr> bool next_sequence(itr first, itr last, int max_bound){ itr now = last; while(now != first){ now--; (*now)++; if((*now) == max_bound){ (*now) = 0; }else{ return true; } } return false; }

vector<int> factor(int N){
    vector<int> ans;
    for(int i = 2; i * i <= N; ){
        if(N % i == 0){
            ans.push_back(i);
            N /= i;
        }else{
            i++;
        }
    }
    ans.push_back(N);
    sort(all(ans));
    return ans;
}

int factor2(int N){
    int ans = 0;
    for(int i = 1; i * i <= N; i++){
        if(N % i == 0){
            if(i * i == N){
                ans += 1;
            }else{
                ans += 2;
            }
        }
    }
    return ans;
}

int main(){
    int N, K;
    cin >> N >> K;
    vector<int> facts = factor(N);
    int ans = 0, ans_sz = -1;
    for(int i = 2; i < N; i++){
        vector<int> this_fact = factor(i), fact2 = facts;
        int sz = factor2(i);
        int count = 0;
        while(this_fact.size() && fact2.size()){
            if(this_fact.back() < fact2.back()){
                fact2.pop_back();
            }else if(this_fact.back() > fact2.back()){
                this_fact.pop_back();
            }else{
                count++;
                fact2.pop_back();
                this_fact.pop_back();
            }
        }
        if(count >= K && ans_sz < sz){
            ans_sz = sz;
            ans = i;
        }
    }
    assert(ans);
    cout << ans << endl;
}