#include <bits/stdc++.h>
using namespace std;
#include <atcoder/dsu>
void summon()
{
	int L,R; cin>>L>>R;
	vector<tuple<int,int,int>> edges;
	for(int i=L; i<R; ++i) edges.push_back({1,i,i+1});
	for(int i=L; i<R; ++i)
		for(int j=i+i; j<=R; j+=i)
			edges.push_back({0,i,j});
	sort(edges.begin(),edges.end());
	int ans=0;
	atcoder::dsu uf(R+1);
	for(auto[w,u,v]:edges)
		if(!uf.same(u,v))
		{
			uf.merge(u,v);
			ans+=w;
		}
	cout<<ans<<"\n";
}
int main()
{
	summon();
}