#include<iostream>
#include<cmath>
using namespace std;
int a[1000005] , cnt , y , c;
int main()
{
    int m , n;
    cin >> m >> n;
    for (int i = 2;i <= sqrt(n);i++)
    {
        c = n / i;
        for (int j = c;j >= 2;j--)
        {
            y = j * i;
            if (y < m)
                break;
            else
                a[y - m] = 1;
        }
    }
    for (long long i = m;i <= n;i++)
    {
        if (!a[i - m])
            cnt++;
    }
    cout << cnt;
    return 0;
}