import math

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

total = 0.0

d_min = math.floor((start - 30) / 24)
d_max = math.ceil((end - 18) / 24)

for d in range(d_min, d_max + 1):
    s_night = 18 + 24 * d
    e_night = 30 + 24 * d
    overlap_start = max(start, s_night)
    overlap_end = min(end, e_night)
    if overlap_start < overlap_end:
        total += overlap_end - overlap_start

print(total)