8483: Walk

内存限制:128 MB 时间限制:3 S
题面:传统 评测方式:文本比较 上传者:
提交:4 通过:1

题目描述

There is currently a grid of n × m. You have to walk start at (1,k 1 )(∀1 ≤ k 1 ≤ m),end at
(n,k 2 )(∀1 ≤ k 2 ≤ m).For every possible path, there will be a value V .The initial value of V is f[k 1 ]
when you start at (1,k 1 ).When you reach (x,y), the value will become V ×f[y].When you are located at
(x,y) , you can walk to (x + 1,P)(P ≤ y + S(S(S(y))))
Where S(x) = blog2(max(1,x)))c
Calculate the sum of the value of all the ways module 998244353.
Two ways A,B think different if ∃(x,y), A passes (x,y) but B not.

输入格式

The first line contains two integers n,m
The second line contains m integers f 1 ,f 2 ,...,f m
1 ≤ n,m ≤ 10 5 ,0 ≤ f i ≤ 10 9

输出格式

print one integer — the answer to the problem.

输入样例 复制

5 4
1 2 3 4

输出样例 复制

7770

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