import math

T, S, D = map(int, input().split())
t = D / S
s = T
e = s + t

k_min = math.floor((s - 30) / 24) + 1
k_max = math.floor((e - 18) / 24)

total = 0.0

for k in range(k_min, k_max + 1):
    L_k = 18 + 24 * k
    R_k = 30 + 24 * k
    overlap_start = max(s, L_k)
    overlap_end = min(e, R_k)
    if overlap_start < overlap_end:
        total += overlap_end - overlap_start

print(total)