import math

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

total = 0.0

k_min = math.floor((start - 30) / 24)
k_max = math.ceil((end - 18) / 24)

for k in range(k_min, k_max + 1):
    night_start = 18 + 24 * k
    night_end = 30 + 24 * k
    overlap_start = max(start, night_start)
    overlap_end = min(end, night_end)
    if overlap_start < overlap_end:
        total += overlap_end - overlap_start

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