L,R = map(int,input().split())

parent = list(range(R+1))
import sys
sys.setrecursionlimit(10 ** 8)
def find(i):
    if parent[i] == i:return i
    parent[i] = find(parent[i])
    return parent[i]
def unite(i,j):
    I = find(i)
    J = find(j)
    if I == J:return False
    parent[I] = J
    parent[i] = J
    return True
def isSame(i,j):
    return find(i) == find(j)

for i in range(L,R+1):
    for j in range(i * 2,R+1,i):
        unite(i,j)
ans = 0
s = set()
for i in range(L,R+1):
    s.add(find(i))
print(len(s) - 1)