#include <iostream>
#include <vector>
using namespace std;
vector<int> su;
bool pan(int n)
{
    if(n==1){
        return 1;
    }
    for (int i = 0; i < su.size(); i++) {
        if (n % su[i] == 0 || su[i] * su[i] > n) {
            return 0;
        }
    }
    su.push_back(n);
    return 1;
}
int main()
{
    int begn, ends;
    cin >> begn >> ends;
    int bgnum=1,ednum=1;
    /*if(pan(begn)==1){
        bgnum--;
    }*/
    for (int i = 2; i * i <= ends; i++) {
        if (pan(i) == 1) {
            if (i * i <= begn) {
                bgnum+=begn/i+i-2;
            }
            ednum+=ends/i+i-2;
        }
    }

    cout<<ends-ednum-begn+bgnum;
}