t, s, d = map(int, input().split())
h = d / s
day, h = divmod(h, 24)
ans = day * 12
t = (t - 18) % 24
if t < 12:
    ans += min(12, t + h) - t
if t + h >= 24:
    ans += min(36, t + h) - 24
print(f'{ans:.12f}')