AtCoder Regular Contest 148
E
≥ K
AtCoder
⌀ 2785
原题
← DF →
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Problem Statement

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You are given a sequence of length $N$, $A = (A_1, ..., A_N)$, and an integer $K$. How many permutations of $A$ are there such that no two adjacent elements sum to less than $K$? Find the count modulo $998244353$.

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Constraints

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  • $2 \leq N \leq 2 \times 10^5$
  • $0 \leq K \leq 10^9$
  • $0 \leq A_i \leq 10^9$
  • All values in the input are integers.
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Input

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The input is given from Standard Input in the following format:

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N K
A_1 A_2 \dots A_N

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Output

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Print the answer.

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样例

Input #1
4 5
1 2 3 4
Output #1
4
The following four permutations satisfy the condition: - $(1, 4, 2, 3)$ - $(1, 4, 3, 2)$ - $(2, 3, 4, 1)$ - $(3, 2, 4, 1)$
Input #2
4 3
1 2 3 3
Output #2
12
There are $12$ permutations of $A$, all of which satisfy the condition.
Input #3
10 7
3 1 4 1 5 9 2 6 5 3
Output #3
108
题目信息
题号
arc148_e
时间限制
2 s
内存限制
1024 MB

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