#include <iostream>
#include <algorithm>
using namespace std;
bool pan[1000001]={0};
int main()
{
    int begn, ends;
    cin >> begn >> ends;
    for (int i = 2; i * i <= ends; i++) {
        for(int j=ends/i;i*j>=begn&&j!=1;j--){
            pan[i*j-begn]=1;
        }
    }
    int ans=0;
    for(int i=0;i<=ends-begn;i++){
        if(pan[i]==0){
            ans++;
            //cout<<begn+i<<" ";
        }
    }
    cout<<ans;
}