#include <bits/stdc++.h>

using namespace std;
 
bool check (long long x)
{
    for (long long i = 2; i <= sqrt(x); ++i)
    if (x % i == 0) return false;
    return x > 1;
}
long long n, m, d = 0, d1 = 0;
int main() {
    cin >> n >> m;
    for (long long i = 2; i <= sqrt(m); ++i)
    {
        if (check(i) and (i * i >= n and i * i <= m)) d1++;
    }
    cout << d1;
    return 0;
}

#include <bits/stdc++.h>
using namespace std;

bool is_prime(long long x) {
    if (x <= 1) return false;
    if (x == 2) return true;
    if (x % 2 == 0) return false;
    for (long long i = 3; i * i <= x; i += 2) {
        if (x % i == 0) return false;
    }
    return true;
}

int main() {
    long long n, m;
    cin >> n >> m;
    
    int count = 0;
    long long p = 2;
    while (p * p <= m) {
        if (is_prime(p)) {
            long long p_squared = p * p;
            if (p_squared >= n && p_squared <= m) {
                count++;
            }
        }
        p++;
    }
    
    cout << count << endl;
    
    return 0;
}