Suppose you are given a 1-indexed sequence $a$ of non-negative integers, whose length is $n$, and two integers $x$, $y$. In consecutive $t$ seconds ($t$ can be any positive real number), you can do one of the following operations:
- Select
$1\le i \lt n$, decrease$a_i$by$x\cdot t$, and decrease$a_{i+1}$by$y\cdot t$. - Select
$1\le i \lt n$, decrease$a_i$by$y\cdot t$, and decrease$a_{i+1}$by$x\cdot t$.
Define the minimum amount of time (it might be a real number) required to make all elements in the sequence less than or equal to $0$ as $f(a)$.
For example, when $x=1$, $y=2$, it takes $3$ seconds to deal with the array $[3,1,1,3]$. We can:
- In the first
$1.5$seconds do the second operation with$i=1$. - In the next
$1.5$seconds do the first operation with$i=3$.
We can prove that it's not possible to make all elements less than or equal to $0$ in less than $3$ seconds, so $f([3,1,1,3])=3$.
Now you are given a 1-indexed sequence $b$ of positive integers, whose length is $n$. You are also given positive integers $x$, $y$. Process $q$ queries of the following two types:
1 k v: change$b_k$to$v$.2 l r: print$f([b_l,b_{l+1},\dots,b_r])$.
Input
The first line of input contains two integers $n$ and $q$ ($2\le n\le 2\cdot 10^5$, $1\le q\le 2\cdot 10^5$).
The second line of input contains two integers $x$ and $y$ ($1\le x,y\le 10^6$).
The third line of input contains $n$ integers $b_1,b_2,\ldots,b_n$ ($1\le b_i\le 10^6$).
This is followed by $q$ lines. Each of these $q$ lines contains three integers. The first integer $op$ is either $1$ or $2$.
- If it is
$1$, it is followed by two integers$k$,$v$($1\le k\le n$,$1\le v\le 10^6$). It means that you should change$b_k$to$v$. - If it is
$2$, it is followed by two integers$l$,$r$($1\le l \lt r\le n$). It means that you should print$f([b_l,b_{l+1},\dots,b_r])$.
Output
For each query of type $2$, print one real number — the answer to the query. Your answer is considered correct if its absolute error or relative error does not exceed $10^{-9}$.
Note
Let's analyse the sample.
In the first query, we are asked to compute $f([3,1,1,4])$. The answer is $3.5$. One optimal sequence of operations is:
- In the first
$1.5$seconds do the second operation with$i=1$. - In the next
$2$seconds do the first operation with$i=3$.
In the third query, we are asked to compute $f([1,1,1])$. The answer is $1$. One optimal sequence of operations is:
- In the first
$0.5$seconds do the second operation with$i=1$. - In the next
$0.5$seconds do the first operation with$i=2$.
样例
4 3
1 2
3 1 1 4
2 1 4
1 1 1
2 1 3
3.500000000000000
1.000000000000000
题面与样例版权归 Codeforces 及出题人所有;中文翻译由 AI 生成(CI 管线),如有出入请以原文为准。