def calculate_night_hours(s1, e1):
    overlap = 0.0
    # Check overlap with 0-6 hours
    start = max(s1, 0.0)
    end = min(e1, 6.0)
    if start < end:
        overlap += end - start
    # Check overlap with 18-24 hours
    start = max(s1, 18.0)
    end = min(e1, 24.0)
    if start < end:
        overlap += end - start
    return overlap

T, S, D = map(int, input().split())
travel_time = D / S
days = int(travel_time // 24)
remainder = travel_time % 24

total_night = days * 12

start = T
end = start + remainder

if end > 24:
    # Split into two intervals
    part1_start = start
    part1_end = 24.0
    part2_start = 0.0
    part2_end = end - 24.0
    overlap1 = calculate_night_hours(part1_start, part1_end)
    overlap2 = calculate_night_hours(part2_start, part2_end)
    total_remainder = overlap1 + overlap2
else:
    total_remainder = calculate_night_hours(start, end)

total_night += total_remainder

print("{0:.15f}".format(total_night))