#pragma region Macros
// #pragma GCC target("avx2")
#pragma GCC optimize("O3")
#include <bits/stdc++.h>
#define rep(i, n) for (long long i = 0; i < (n); i++)
#define rrep(i, n) for (long long i = (n - 1); i >= 0; i--)
#define ALL(v) v.begin(), v.end()
#define endl "\n"
#define fi first
#define se second
#define popcount(bit) __builtin_popcount(bit)
#define popcountll(bit) __builtin_popcountll(bit)
#define pb push_back
#define eb emplace_back
using namespace std;
using P = pair<int, int>;
using PL = pair<long long, long long>;
using Graph = vector<vector<int>>;
typedef long long ll;
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};
const int fx[8] = {0, 1, 1, 1, 0, -1, -1, -1};
const int fy[8] = {1, 1, 0, -1, -1, -1, 0, 1};
template <typename T>
const auto INF = numeric_limits<T>::max()/2;

namespace PrimeCounting {
using i64 = long long;
static inline i64 my_div(i64 n, i64 p) { return double(n) / p; };

__attribute__((target("avx2"), optimize("O3", "unroll-loops"))) i64 prime_counting(i64 N) {
    i64 N2 = sqrt(N);
    i64 NdN2 = my_div(N, N2);

    vector<i64> hl(NdN2);
    for(int i = 1; i < NdN2; i++) hl[i] = my_div(N, i) - 1;

    vector<int> hs(N2 + 1);
    iota(begin(hs), end(hs), -1);

    for(int x = 2, pi = 0; x <= N2; ++x) {
        if(hs[x] == hs[x - 1]) continue;
        i64 x2 = i64(x) * x;
        i64 imax = min<i64>(NdN2, my_div(N, x2) + 1);
        i64 ix = x;
        for(i64 i = 1; i < imax; ++i) {
            hl[i] -= (ix < NdN2 ? hl[ix] : hs[my_div(N, ix)]) - pi;
            ix += x;
        }
        for(int n = N2; n >= x2; n--) { hs[n] -= hs[my_div(n, x)] - pi; }
        ++pi;
    }
    return hl[1];
}

} // namespace PrimeCounting

/**
 * @brief 素数カウント( $\mathrm{O}(\frac{N^{\frac{3}{4}}}{\log N})$・高速化版)
 * @docs docs/multiplicative-function/prime-counting.md
 */


int main() {
  ll l, r;
  cin >> l >> r;
  auto f = [&](ll l, ll r) { return PrimeCounting::prime_counting(r) - (l > 1 ? PrimeCounting::prime_counting(l - 1) : 0); };
  ll ans = f(l, r);
  if(r > l)ans += f(2* l + 1, 2 * r-1);
  cout << ans << endl;
}