import sys
input=lambda: sys.stdin.readline().rstrip()
l,r=map(int,input().split())
D=[1]*(r+1)
for i in range(r+1):
  if i<l:
    D[i]=0
  else:
    mul=2
    while mul*i<=r:
      D[mul*i]=0
      mul+=1
print(sum(D)-1)