#include <fstream>
#include <cmath>

using namespace std;
ifstream fin("divprim.in");
ofstream fout("divprim.out");

const int Nmax = 1000000;
long long n, k, i, j, nr[Nmax+5];
bool ok, v[Nmax+5];

void ciur()
{
    v[0] = 1;
    v[1] = 1;
    for(i=2; i<=Nmax; i++)
        if(!v[i])
        {
            nr[i] = 1;
            for(j=2; i*j<=Nmax; j++)
                {
                    v[i*j] = 1;
                    nr[i*j]++;
                }
        }
}

int main()
{
    fin >> n >> k;
    ciur();
    while(!ok && n>=0)
    {
        if(nr[n]==k)
            ok = 1;
        n--;
    }
    n++;
    fout << n;
    fin.close();
    fout.close();
    return 0;
}