CF1821F.Timber

普及/提高-

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题目描述

There is a beautiful alley with trees in front of a shopping mall. Unfortunately, it has to go to make space for the parking lot.

The trees on the alley all grow in a single line. There are nn spots for trees, index 00 is the shopping mall, index n+1n+1 is the road and indices from 11 to nn are the spots for trees. Some of them are taken — there grow trees of the same height kk . No more than one tree grows in each spot.

When you chop down a tree in the spot xx , you can make it fall either left or right. If it falls to the left, it takes up spots from xkx-k to xx , inclusive. If it falls to the right, it takes up spots from xx to x+kx+k , inclusive.

Let mm trees on the alley grow in some spots x1,x2,,xmx_1, x_2, \dots, x_m . Let an alley be called unfortunate if all mm trees can be chopped down in such a way that:

  • no tree falls on the shopping mall or the road;
  • each spot is taken up by no more than one fallen tree.

Calculate the number of different unfortunate alleys with mm trees of height kk . Two alleys are considered different if there is a spot yy such that a tree grows in yy on the first alley and doesn't grow in yy on the second alley.

Output the number modulo 998244353998\,244\,353 .

输入格式

The only line contains three integers n,mn, m and kk ( 1m,kn31051 \le m, k \le n \le 3 \cdot 10^5 ) — the number of spots for the trees, the number of trees and the height of each tree.

输出格式

Print a single integer — the number of different unfortunate alleys with mm trees of height kk , modulo 998244353998\,244\,353 .

输入输出样例

  • 输入#1

    6 1 4

    输出#1

    4
  • 输入#2

    5 2 2

    输出#2

    0
  • 输入#3

    6 2 2

    输出#3

    4
  • 输入#4

    15 3 2

    输出#4

    311
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