#include "bits/stdc++.h"
//#include "atcoder/all"
using namespace std;
//using namespace atcoder;
//using mint = modint1000000007;
//const int mod = 1000000007;
//using mint = modint998244353;
//const int mod = 998244353;
//const int INF = 1e9;
//const long long LINF = 1e18;
//const bool debug = false;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n-1); i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r-1);i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define endl "\n"
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }
//n以下の素数の個数
int isqrt(long long n) { return sqrtl(n); }
long long prime_pi(const long long N) {
	if (N <= 1) return 0;
	if (N == 2) return 1;
	const int v = isqrt(N);
	int s = (v + 1) / 2;
	vector<int> smalls(s); for (int i = 1; i < s; ++i) smalls[i] = i;
	vector<int> roughs(s); for (int i = 0; i < s; ++i) roughs[i] = 2 * i + 1;
	vector<long long > larges(s); for (int i = 0; i < s; ++i) larges[i] = (N / (2 * i + 1) - 1) / 2;
	vector<bool> skip(v + 1);
	const auto divide = [](long long n, long long d) -> int { return double(n) / d; };
	const auto half = [](int n) -> int { return (n - 1) >> 1; };
	int pc = 0;
	for (int p = 3; p <= v; p += 2) if (!skip[p]) {
		int q = p * p;
		if (((long long)q) * q > N) break;
		skip[p] = true;
		for (int i = q; i <= v; i += 2 * p) skip[i] = true;
		int ns = 0;
		for (int k = 0; k < s; ++k) {
			int i = roughs[k];
			if (skip[i]) continue;
			long long d = ((long long)i) * p;
			larges[ns] = larges[k] - (d <= v ? larges[smalls[d >> 1] - pc] : smalls[half(divide(N, d))]) + pc;
			roughs[ns++] = i;
		}
		s = ns;
		for (int i = half(v), j = ((v / p) - 1) | 1; j >= p; j -= 2) {
			int c = smalls[j >> 1] - pc;
			for (int e = (j * p) >> 1; i >= e; --i) smalls[i] -= c;
		}
		++pc;
	}
	larges[0] += ((long long)s + 2 * (pc - 1)) * (s - 1) / 2;
	for (int k = 1; k < s; ++k) larges[0] -= larges[k];
	for (int l = 1; l < s; ++l) {
		int q = roughs[l];
		long long M = N / q;
		int e = smalls[half(M / q)] - pc;
		if (e < l + 1) break;
		long long t = 0;
		for (int k = l + 1; k <= e; ++k) t += smalls[half(divide(M, roughs[k]))];
		larges[0] += t - ((long long)e - l) * (pc + l - 1);
	}
	return larges[0] + 1;
}

int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	long long l, r; cin >> l >> r;
	long long ans = 0;
	ans += prime_pi(r) - prime_pi(l - 1);
	if (l != r)ans += prime_pi(r * 2 - 1) - prime_pi(l * 2);
	cout << ans << endl;
	return 0;
}