import sys
input = sys.stdin.readline
L, R = map(int, input().split())
s = set([x for x in range(L, R + 1)])
#print(s)
for x in range(L, R + 1):
  for y in range(2 * x, R + 1, x):
    s.discard(y)
print(len(s) - 1)