CF799A Carrot Cakes

一共需要烤 $n$ 个蛋糕，用一个烤箱烤 $k$ 个蛋糕需要 $t$ 分钟。现有一个烤箱，可以再用 $d$ 分钟建一个。建烤箱时正在建的烤箱不能工作，但另一个烤箱可以。问：新建烤箱烤完 $n$ 个蛋糕的时间是否比不新建要严格快（即不能等于）？

一行，四个数，分别是 $n$ , $t$ , $k$ , $d$。

若比它要快，输出```YES```；否则输出```NO```。

In the first example it is possible to get $ 8 $ cakes in $ 12 $ minutes using one oven. The second oven can be built in $ 5 $ minutes, so after $ 6 $ minutes the first oven bakes $ 4 $ cakes, the second oven bakes $ 4 $ more ovens after $ 11 $ minutes. Thus, it is reasonable to build the second oven. In the second example it doesn't matter whether we build the second oven or not, thus it takes $ 12 $ minutes to bake $ 8 $ cakes in both cases. Thus, it is unreasonable to build the second oven. In the third example the first oven bakes $ 11 $ cakes in $ 3 $ minutes, that is more than needed $ 10 $ . It is unreasonable to build the second oven, because its building takes more time that baking the needed number of cakes using the only oven.