a_b = [int(i) for i in input().split()]
a = a_b[0]
b = a_b[1]

trip = [i+a for i in range(b - a + 1)]
days = [23, 24, 25]

if 23 in trip:
    days.remove(23)
if 24 in trip:
    days.remove(24)
if 25 in trip:
    days.remove(25)

print(len(days))