t, s, d = map(int, input().split())

if 0 <= t <= 6:
    t += 24

drive = d / s
ans = (drive - (30 - t)) // 24

if ans >= 1:
    print(30 - t +  12 * ans)
else:
    if drive > 12:
        print(30 - t)
    else:
        print(drive)