CF1804B.Vaccination

传统题 时间 2000 ms 内存 256 MiB 5 尝试 1 已通过 1 标签

Vaccination

Ethan runs a vaccination station to help people combat the seasonal flu. He analyses the historical data in order to develop an optimal strategy for vaccine usage.

Consider there are nn patients coming to the station on a particular day. The ii-th patient comes at the moment tit_i. We know that each of these patients can be asked to wait for no more than ww time moments. That means the ii-th patient can get vaccine at moments ti,ti+1,,ti+wt_i, t_i + 1, \ldots, t_i + w.

Vaccines come in packs, each pack consists of kk doses. Each patient needs exactly one dose. Packs are stored in a special fridge. After a pack is taken out of the fridge and opened, it can no longer be put back. The lifetime of the vaccine outside the fridge is dd moments of time. Thus, if the pack was taken out of the fridge and opened at moment xx, its doses can be used to vaccinate patients at moments x,x+1,,x+dx, x + 1, \ldots, x + d. At moment x+d+1x + d + 1 all the remaining unused doses of this pack are thrown away.

Assume that the vaccination station has enough staff to conduct an arbitrary number of operations at every moment of time. What is the minimum number of vaccine packs required to vaccinate all nn patients?

Input

The first line of the input contains the number of test cases tt (1t1041 \leq t \leq 10^4). Then follow tt descriptions of the test cases.

The first line of each test case contains four integers nn, kk, dd and ww (1n,k21051 \leq n, k \leq 2 \cdot 10^5, 0d,w1060 \leq d, w \leq 10^6). They are the number of patients, the number of doses per vaccine pack, the number of moments of time the vaccine can live outside the fridge, and the number of moments of time each of the patients can wait, respectively.

The second line of each test case contains a non-decreasing sequence t1,t2,,tnt_1, t_2, \ldots, t_n (0t1t2tn1060 \leq t_1 \leq t_2 \leq \ldots \leq t_n \leq 10^6). The ii-th element of this sequence is the moment when the ii-th patient comes to the vaccination station.

It is guaranteed that the sum of nn over all test cases won't exceed 21052 \cdot 10^5.

Output

Output one integer, the minimum number of vaccine packs required to vaccinate all nn patients.

Note

In the first example, the first pack can be opened at moment 11 to vaccinate patient 11. The vaccine is durable enough to be used at moments 22 and 33 for patients 22 and 33, respectively. Then the staff needs to ask patients 44 and 55 to wait for moment 1313. At moment 1313 the staff opens the second vaccine pack and serves patients 44 and 55. Finally, the last patient comes at moment 1818 and immediately gets the last dose of the second pack while it is still fine.

In the second example, the vaccine should be used exactly at the moment it is taken out of the fridge. Moreover, all the patients want to be served at exactly the same moment they come. That means the staff needs to open two packs at moment 33 and use five doses on patients 11, 22, 33, 44, and 55. There will be three doses left ouf of these two packs but they can't be used for patient 66. When patient 66 comes at moment 44 the staff needs to open a new pack just to use only one dose out of it.

Samples

5
6 3 5 3
1 2 3 10 11 18
6 4 0 0
3 3 3 3 3 4
9 10 2 2
0 1 2 3 4 5 6 7 8
3 10 3 6
10 20 30
5 5 4 4
0 2 4 6 8
2
3
2
3
1

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