T, S, D = map(int, input().split())
travel_time = D / S
start = T
end = start + travel_time

total = 0.0
k = 0

while True:
    night_start = 18 + 24 * k
    night_end = night_start + 12  # 18:00 to 06:00 next day (12 hours)
    
    overlap_start = max(start, night_start)
    overlap_end = min(end, night_end)
    
    if overlap_start < overlap_end:
        total += overlap_end - overlap_start
    
    # Check next night period
    next_k = k + 1
    next_night_start = 18 + 24 * next_k
    if next_night_start >= end:
        break
    k = next_k

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