T, S, D = map(int, input().split())
time = D / S
if 6 <= T < 18:
    if 6 <= T + time < 18:
        print(0)
    else:
        print(T + time - 18)
else:
    if 6 <= T + time < 18:
        print((T + time) % 24 - 6)
    else:
        print(time)