#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i = 0; i < (n);i++)
#define sz(x) int(x.size())
typedef long long ll;
typedef pair<int,int> P;
struct UnionFind{
  vector<int> data;
  int __size;
  UnionFind(int sz) {
  data.assign(sz, -1);
  __size = sz;
  }
 
  bool unite(int x, int y) {
    x = find(x), y = find(y);
    if(x == y) return (false);
    if(data[x] > data[y]) swap(x, y);//親は負でサイズを保存
    __size--;
    data[x] += data[y];
    data[y] = x;
    return (true);
  }
 
  int find(int k) {
    if(data[k] < 0) return (k);
    return (data[k] = find(data[k]));
  }

  bool same(int x, int y){
    return find(x) == find(y);
  }
 
  int size(int k) {
    return (-data[find(k)]);
  }

  int union_count() {
    return (__size);
  }
};
int main() {
  int l, r;
  cin >> l >> r;

  int n = r - l + 1;
  UnionFind uf(n);
  for (int i = 0; i < n; i++) {
    int d = i + l;
    for (ll j = i + d; j < n; j += d) {
      uf.unite(i, j);
    }
  }
  cout << uf.union_count() - 1 << endl;
  return 0;
}