# No.773 コンテスト
a, b = [int(i) for i in input().split()]
contests = [23, 24, 25]
trips = [i for i in range(a, b + 1)]

can_perticipate = 0

for i in contests:
    if i not in trips:
        can_perticipate += 1

print(can_perticipate)