#include <stdio.h>

#define HASH 1000003
const int H_Mod = HASH;

typedef struct List {
	struct List *next;
	long long v, ans;
} list;

// N <= 10^11
long long prime_count(long long N)
{
	if (N <= 1) return 0;
	
	int h, k;
	long long i, ii, key[1000000], tmp;
	list *hash[HASH] = {}, d[1000000], *p, *pp;
	for (i = 1, k = 0; i * i <= N; i++) {
		key[k] = N / i;
		d[k].v = key[k];
		d[k].ans = key[k] - 1;
		h = key[k] % H_Mod;
		d[k].next = hash[h];
		hash[h] = &(d[k++]);
	}
	for (i = d[k-1].v - 1; i > 0; i--) {
		key[k] = i;
		d[k].v = i;
		d[k].ans = i - 1;
		d[k].next = hash[i];
		hash[i] = &(d[k++]);
	}
	
	for (i = 2; i * i <= N; i++) {
		for (p = hash[i]; p != NULL; p = p->next) if (p->v == i) break;
		for (pp = hash[i-1]; pp != NULL; pp = pp->next) if (pp->v == i - 1) break;
		if (p->ans <= pp->ans) continue;
		for (k = 0, ii = i * i; key[k] >= ii; k++) {
			tmp = key[k] / i;
			h = tmp % H_Mod;
			for (p = hash[h]; p != NULL; p = p->next) if (p->v == tmp) break;
			d[k].ans -= p->ans - pp->ans;
		}
	}
	
	return d[0].ans;
}

int main()
{
	long long L, R;
	scanf("%lld %lld", &L, &R);
	printf("%lld\n", prime_count(R) - prime_count(L - 1) + ((L < R)? prime_count(R * 2 - 1) - prime_count(L * 2): 0));
	fflush(stdout);
	return 0;
}