l,r = map(int,input().split())

class UnionFind:
    def __init__(self, n):
        self.par = [i for i in range(n+1)]
        self.rank = [0] * (n+1)
        self.size = [1 for _ in range(n+1)]
    # 検索
    def find(self, x):
        if self.par[x] == x:
            return x
        else:
            self.par[x] = self.find(self.par[x])
            return self.par[x]
    # 併合
    def union(self, x, y):
        x = self.find(x)
        y = self.find(y)
        if self.rank[x] < self.rank[y]:
            self.par[x] = y
            self.size[y] += self.size[x]
        else:
            self.par[y] = x
            self.size[x] += self.size[y]
        if self.rank[x] == self.rank[y]:
            self.rank[x] += 1
    # 同じ集合に属するか判定
    def same_check(self, x, y):
        return self.find(x) == self.find(y)

n = r+1
ki = UnionFind(n)
for i in range(l,r+1):
    for j in range(i+i,r+1,i):
        if not ki.same_check(i,j):
            ki.union(i,j)

ss = set()

for i in range(l,r+1):
    ss.add(ki.find(i))

print(len(ss)-1)