# zerofill half-hour intervals
dinDons = [0 for x in range(48)]

for hour in range(24):
	curHalf = hour*2
	for minute in range(60):
		if minute == 30:
			dinDons[curHalf+1] += 1
	curHour = hour % 12
	dinDons[curHalf] = curHour if curHour else 12

# evil cicling =)
dinDons *= 10

# zerofill all intervals
intervals = [0 for x in range(48)]

for i in range(len(intervals)):
	for j in range(10000//30):
		intervals[i] += dinDons[i+j]

print(max(intervals))