T, S, D = map(int, input().split())


def f(x, now, time):
    return min(time - now, (D - x) / S)


x = 0
t = T
ans = 0
while x < D:
    if t < 6:
        k = f(x, t, 6)
        ans += k
        x += S * k
        t += k
    elif t < 18:
        k = f(x, t, 18)
        x += S * k
        t += k
    elif t < 24:
        k = f(x, t, 24)
        ans += k
        x += S * k
        t += k
        t %= 24

print(ans)