import sys
input=lambda: sys.stdin.readline().rstrip()
l,r=map(int,input().split())
n=r-l+1
par=[-1]*n

def find(x):
  if par[x]<0:
    return x
  else:
    par[x]=find(par[x])
    return par[x]

def unite(x,y):
  x=find(x)
  y=find(y)
  if x==y:
    return False
  else:
    if par[x]>par[y]:
      x,y=y,x
    par[x]+=par[y]
    par[y]=x
    return True

def same(x,y):
  return find(x)==find(y)

def size(x):
  return -par[find(x)]

for i in range(l,r+1):
  mul=2
  while mul*i<=r:
    unite(i-l,i*mul-l)
    mul+=1
ct=0
for i in range(n):
  if par[i]<0:
    ct+=1
print(ct-1)