#include <bits/stdc++.h>

using namespace std;
#define rep(i,n) for (int i = 0; i < (int)(n); ++i)
#define rrep(i,n) for (int i = (int)(n-1); i >= 0; --i)
#define Rep(i,a,b) for (int i = a; i < b; ++i)
#define rRep(i,a,b) for (int i = a; i > b; --i)
#define fore(i,a) for(auto &i:a)
#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()
#define Bit(x,i) (((x)>>(i))&1)
using ll = long long;
using vi = vector<int>;
using vll = vector<long long>;
using vvi = vector<vi>;
using vvll = vector<vll>;
using vb = vector<bool>;
using vs = vector<string>;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }
struct settings{settings(){ios_base::sync_with_stdio(0); cin.tie(0); cout<<fixed<<setprecision(15);};}settingss;
const double PI = acos(-1);
const int INF = 1001001001;
const ll LINF = 1001001001001001001LL;

struct UnionFind {
  vector<int> par;
  UnionFind() { }
  UnionFind(int n) : par(n, -1) {}
  void init(int n) { par.assign(n, -1); }
  int root(int x) {
    if (par[x] < 0) return x;
    else return par[x] = root(par[x]);
  }
  bool issame(int x, int y) {
    return root(x) == root(y);
  }
  bool merge(int x, int y) {
    x = root(x); y = root(y);
    if (x == y) return false;
    if (par[x] > par[y]) swap(x, y);
    par[x] += par[y];
    par[y] = x;
    return true;
  }
  int size(int x) {
    return -par[root(x)];
  }
};

UnionFind uf(200100);
struct Edge {
  ll frm, to, cost;
  bool operator<(const Edge& o) const {
    return cost < o.cost;
  }
};
struct Graph {
  vector<Edge> es;
  ll kruskal() {
    sort(es.begin(), es.end());
    ll min_cost = 0;
    rep(ei, es.size()) {
      Edge& e = es[ei];
      if (!uf.issame(e.frm, e.to)) {
        min_cost += e.cost;
        uf.merge(e.frm, e.to);
      }
    }
    return min_cost;
  }
};

Graph g;

int main() {
  int L, R; cin >> L >> R;
  Rep(i, L, R) {
    Edge e;
    e.frm = i; e.to = i+1; e.cost = 1;
    g.es.push_back(e);
  }
  Rep(i, L, R+1) {
    for(int j = 2; i*j <= R; ++j) {
      Edge e;
      e.frm = i; e.to = i*j; e.cost = 0;
      g.es.push_back(e);
    }
  }
  cout << g.kruskal() << endl;
}