from collections import defaultdict


class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1]*n
        self.rank = [0]*n

    def find(self, x):
        if self.parents[x] < 0:
            return x
        else:
            return self.find(self.parents[x])

    def size(self, x):
        return -self.parents[self.find(x)]

    def union(self, x, y):
        x = self.find(x)
        y = self.find(y)
        if x == y:
            return
        if self.rank[x] < self.rank[y]:
            x, y = y, x
        self.parents[x] += self.parents[y]
        self.parents[y] = x
        if self.rank[x] == self.rank[y]:
            self.rank[x] += 1

    def root(self):
        return [i for i in range(self.n) if self.parents[i] < 0]

    def allgroup_members(self):
        members = defaultdict(set)
        for m in range(self.n):
            members[self.find(m)].add(m)
        return members


L, R = map(int, input().split())
n = R-L+1
uf = UnionFind(n)
for i in range(L, R+1):
    for j in range(i, R+1, i):
        uf.union(i-L, j-L)

D = uf.allgroup_members()
print(len(D)-1)