#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
typedef pair<ll, ll> P;
typedef vector<ll> VI;
typedef vector<VI> VVI;
const ll MOD = 1000000007;
const ll INF = 4611686018427387903;
#define REP(i, n) for (int i = 0; i < n; i++)
#define ALL(v) v.begin(), v.end()

VVI edge(214514, VI(0));
vector<bool> f(214514,0);
void dfs(int v, int p) {
	for (auto to:edge[v]) {
		if (to!=p&&!f[to]){
			f[to]=1;
			dfs(to, v);
		}
	}
}

int main(){
	int l, r; cin >> l >> r;
	for(int i=l;i<=r;i++){
		for(int j=i*2;j<=r;j+=i){
			edge[i].push_back(j);
			edge[j].push_back(i);
		}
	}
	int ans=0;
	for(int i=l;i<=r;i++){
		if(!f[i]){
			ans++;
			f[i]=1;
			dfs(i,-1);
		}
	}
	cout << ans-1 << endl;
	return 0;
}