T, S, D = map(int, input().split())
time_h = D / S
n = int(time_h // 24)
r = time_h % 24

total = n * 12  # Full days contribute 12 hours each

if r > 1e-9:
    def calculate_overlap(T, r):
        overlap = 0.0
        start = T
        end = T + r

        # Night period on the departure day (18:00 to 24:00)
        night1_start = 18
        night1_end = 24
        part1_start = max(start, night1_start)
        part1_end = min(end, night1_end)
        if part1_end > part1_start:
            overlap += part1_end - part1_start

        # Night period on the arrival day (00:00 to 06:00)
        night2_start = 0
        night2_end = 6
        if end > 24:
            # Check next day's night period (00:00 to 06:00)
            part2_start = max(start, 24 + night2_start)
            part2_end = min(end, 24 + night2_end)
        else:
            # Check same day's night period (00:00 to 06:00)
            part2_start = max(start, night2_start)
            part2_end = min(end, night2_end)
        if part2_end > part2_start:
            overlap += part2_end - part2_start

        return overlap

    overlap = calculate_overlap(T, r)
    total += overlap

print(total)