#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <stdbool.h>

int solution(int l, int r) {
    // Find all primes up to sqrt(r) using Sieve of Eratosthenes
    int limit = (int)sqrt(r) + 1;
    bool *isPrime = (bool*)malloc((limit + 1) * sizeof(bool));
    for (int i = 0; i <= limit; i++) {
        isPrime[i] = true;
    }
    isPrime[0] = isPrime[1] = false;
    
    for (int i = 2; i <= (int)sqrt(limit); i++) {
        if (isPrime[i]) {
            for (int j = i * i; j <= limit; j += i) {
                isPrime[j] = false;
            }
        }
    }
    
    // Count special numbers (squares of primes) in range [l, r]
    int specialCount = 0;
    for (int p = 2; p <= limit; p++) {
        if (isPrime[p]) {
            long long square = (long long)p * p;
            if (l <= square && square <= r) {
                specialCount++;
            } else if (square > r) {
                break;
            }
        }
    }
    
    free(isPrime);
    return (r - l + 1) - specialCount;
}

int main() {
    int l, r;
    scanf("%d %d", &l, &r);
    printf("%d\n", solution(l, r));
    return 0;
}