题目描述
Problem Statement
Given is a positive integer M and a sequence of N integers: $A = (A_1,A_2,\ldots,A_N).$ Find the number, modulo 998244353, of sequences of $N+1 integers, X = (X_1,X_2, \ldots, X_{N+1}),$ satisfying all of the following conditions:
- $1\leq X_i\leq M (1\leq i\leq N+1)$
- $A_iX_i\leq X_{i+1} (1\leq i\leq N)$
Input
Input is given from Standard Input in the following format:
N M
$A_1 A_2 \ldots A_N$
Output
Print the number of integer sequences satisfying the conditions, modulo 998244353.
Constraints
- $1\leq N\leq 1000$
- $1\leq M\leq 10^{18}$
- $1\leq A_i\leq 10^9$
- $\prod_{i=1}^N A_i \leq M$
Sample Input 1
2 10
2 3
Sample Output 1
7
Seven sequences below satisfy the conditions.
- (1, 2, 6), (1,2,7), (1,2,8), (1,2,9), (1,2,10), (1,3,9), (1,3,10)
Sample Input 2
2 10
3 2
Sample Output 2
9
Nine sequences below satisfy the conditions.
- (1, 3, 6), (1, 3, 7), (1, 3, 8), (1, 3, 9), (1, 3, 10), (1, 4, 8), (1, 4, 9), (1, 4, 10), (1, 5, 10)
Sample Input 3
7 1000
1 2 3 4 3 2 1
Sample Output 3
225650129
Sample Input 4
5 1000000000000000000
1 1 1 1 1
Sample Output 4
307835847
输入格式
见题面 Input 部分
输出格式
见题面 Output 部分