#include <iostream>
#include <fstream>
using namespace std;

ifstream fin("inversmodular.in");
ofstream fout("inversmodular.out");

int a,b,vec[200010];

int nr_prime_mici()
{
    int i,j,contor = 0;
    for(i=2;i<=b;i++)
    {
        for(j=i+i;j<=b;j=j+i)
            vec[j] = 1;
    }
    for(i=2;i<b;i++)
    {
        if(vec[i]==0)
        {
            contor++;
        }
    }
    return contor;

}

int main()
{
    fin>>a>>b;
    fout<<nr_prime_mici();
    return 0;
}