package main

import (
	"bufio"
	"fmt"
	"os"
	"sort"
	"strconv"
)

var sc = bufio.NewScanner(os.Stdin)
var wr = bufio.NewWriter(os.Stdout)

func out(x ...interface{}) {
	fmt.Fprintln(wr, x...)
}

func getI() int {
	sc.Scan()
	i, e := strconv.Atoi(sc.Text())
	if e != nil {
		panic(e)
	}
	return i
}

func getF() float64 {
	sc.Scan()
	i, e := strconv.ParseFloat(sc.Text(), 64)
	if e != nil {
		panic(e)
	}
	return i
}

func getInts(N int) []int {
	ret := make([]int, N)
	for i := 0; i < N; i++ {
		ret[i] = getI()
	}
	return ret
}

func getS() string {
	sc.Scan()
	return sc.Text()
}

// min, max, asub, absなど基本関数
func max(a, b int) int {
	if a > b {
		return a
	}
	return b
}

func min(a, b int) int {
	if a < b {
		return a
	}
	return b
}

func asub(a, b int) int {
	if a > b {
		return a - b
	}
	return b - a
}

func abs(a int) int {
	if a >= 0 {
		return a
	}
	return -a
}

func lowerBound(a []int, x int) int {
	idx := sort.Search(len(a), func(i int) bool {
		return a[i] >= x
	})
	return idx
}

func upperBound(a []int, x int) int {
	idx := sort.Search(len(a), func(i int) bool {
		return a[i] > x
	})
	return idx
}

type UnionFind struct {
	n   int
	par []int
}

func newUnionFind(n int) *UnionFind {
	uf := new(UnionFind)
	uf.n = n
	uf.par = make([]int, n)
	for i, _ := range uf.par {
		uf.par[i] = -1
	}
	return uf
}
func (uf UnionFind) root(x int) int {
	if uf.par[x] < 0 {
		return x
	}
	uf.par[x] = uf.root(uf.par[x])
	return uf.par[x]
}
func (uf UnionFind) unite(x, y int) {
	rx, ry := uf.root(x), uf.root(y)
	if rx != ry {
		if uf.size(rx) > uf.size(ry) {
			rx, ry = ry, rx
		}
		uf.par[ry] += uf.par[rx]
		uf.par[rx] = ry
	}
}
func (uf UnionFind) same(x, y int) bool {
	return uf.root(x) == uf.root(y)
}
func (uf UnionFind) size(x int) int {
	return -uf.par[uf.root(x)]
}
func (uf UnionFind) groups() [][]int {
	rootBuf, groupSize := make([]int, uf.n), make([]int, uf.n)
	for i := 0; i < uf.n; i++ {
		rootBuf[i] = uf.root(i)
		groupSize[rootBuf[i]]++
	}
	res := make([][]int, uf.n)
	for i := 0; i < uf.n; i++ {
		res[i] = make([]int, 0, groupSize[i])
	}
	for i := 0; i < uf.n; i++ {
		res[rootBuf[i]] = append(res[rootBuf[i]], i)
	}
	result := make([][]int, 0, uf.n)
	for i := 0; i < uf.n; i++ {
		if len(res[i]) != 0 {
			r := make([]int, len(res[i]))
			copy(r, res[i])
			result = append(res, r)
		}
	}
	return result
}

func main() {
	defer wr.Flush()
	sc.Split(bufio.ScanWords)
	sc.Buffer([]byte{}, 1000000)
	// this template is new version.
	// use getI(), getS(), getInts(), getF()
	L, R := getI(), getI()
	uf := newUnionFind(R + 1)
	for i := L; i <= R; i++ {
		for j := i + i; j <= R; j += i {
			uf.unite(i, j)
		}
	}
	cnt := 0
	for i := L; i <= R; i++ {
		if uf.root(i) != uf.root(L) {
			uf.unite(L, i)
			cnt++
		}
	}
	out(cnt)
}