#include <cstdio>
#include <string>
#include <cstring>
#include <cstdlib>
#include <cmath>
#include <algorithm>
#include <vector>
#include <set>
#include <map>
#include <queue>
#include <stack>
#include <list>
#include <iterator>
#include <cassert>
#include <numeric>
#include <functional>
//#include <numeric>
#pragma warning(disable:4996) 
 
typedef long long ll;
typedef unsigned long long ull;
#define MIN(a, b) ((a)>(b)? (b): (a))
#define MAX(a, b) ((a)<(b)? (b): (a))
#define LINF  9223300000000000000
#define LINF2 1223300000000000000
#define INF 2140000000
const long long MOD = 1000000007;
//const long long MOD = 998244353;

using namespace std;

class UF
{
private:
    int         num;
    vector<int> par;
    vector<int> siz;
public:
    //vector<int> val;
public:
    UF(int n): num(n) {
        par.resize(n);
        siz.resize(n);
        //val.resize(n);
        int i;
        for(i=0; i<n; i++) {
            par[i]=i; siz[i]=1;
            //val[i]=0;
        }
    }
	
    int find(int x) {
        if(x==par[x]) return x;
        return par[x] = find(par[x]);
    }

    void unite(int x, int y) {
        x=find(x);
        y=find(y);
        if(x==y) return;
        if(siz[x]<siz[y]) {
            par[x]=y;
            siz[y]=siz[x]+siz[y];
            //val[y]=val[x]+val[y];
        }
        else {
            par[y]=x;
            siz[x]=siz[x]+siz[y];
            //val[x]=val[x]+val[y];
        }
    }

    bool same(int x, int y) {
        return find(x)==find(y);
    }

    int size(int x) {
        return siz[find(x)];
    }

    int ngroup() {
    //int ngroup( int& ans ) {
        int count=0;
        int i;
        for(i=0; i<num; i++) {
            if(par[i]==i) {
                count++;
                //ans += (val[i]? siz[i]: siz[i]-1);
            }
        }
        return count;
    }
};

void solve()
{
    int l, r;
    scanf("%d%d", &l, &r);
    if (l == 1) {
        printf("0\n"); return;
    }

    UF uf(r - l + 1);
    int i;
    for (i = l; i < r / 2 + 3; i++) {
        int curr = i + i;
        while (curr <= r) {
            uf.unite(i-l, curr-l);
            curr += i;
        }
    }
    int ans = 0;
    for (i = 0; i < r-l+1; i++) {
        if (uf.find(i) == i)
            ans++;
    }
    printf("%d\n", ans-1);

    return;
}


int main(int argc, char* argv[])
{
#if 1
    solve();
#else
    int T;
    scanf("%d", &T);
    int t;
    for(t=0; t<T; t++) {
        //printf("Case #%d: ", t+1);
        solve();
    }
#endif
    return 0;
}