Codeforces Round 510 (Div. 2)
E
Vasya and Magic Matrix
Codeforces
2300
原题
← DF →
翻译中…

Vasya has got a magic matrix $a$ of size $n \times m$. The rows of the matrix are numbered from $1$ to $n$ from top to bottom, the columns are numbered from $1$ to $m$ from left to right. Let $a_{ij}$ be the element in the intersection of the $i$-th row and the $j$-th column.

翻译中…

Vasya has also got a chip. Initially, the chip is in the intersection of the $r$-th row and the $c$-th column (that is, in the element $a_{rc}$). Vasya performs the following process as long as possible: among all elements of the matrix having their value less than the value of the element with the chip in it, Vasya randomly and equiprobably chooses one element and moves his chip to this element.

翻译中…

After moving the chip, he adds to his score the square of the Euclidean distance between these elements (that is, between the element in which the chip is now and the element the chip was moved from). The process ends when there are no elements having their values less than the value of the element with the chip in it.

翻译中…

Euclidean distance between matrix elements with coordinates $(i_1, j_1)$ and $(i_2, j_2)$ is equal to $\sqrt{(i_1-i_2)^2 + (j_1-j_2)^2}$.

翻译中…

Calculate the expected value of the Vasya's final score.

翻译中…

It can be shown that the answer can be represented as $\frac{P}{Q}$, where $P$ and $Q$ are coprime integer numbers, and $Q \not\equiv 0~(mod ~ 998244353)$. Print the value $P \cdot Q^{-1}$ modulo $998244353$.

翻译中…

Input

翻译中…

The first line of the input contains two integers $n$ and $m$ $(1 \le n, m \le 1\,000)$ — the number of rows and the number of columns in the matrix $a$.

翻译中…

The following $n$ lines contain description of the matrix $a$. The $i$-th line contains $m$ integers $a_{i1}, a_{i2}, \dots, a_{im} ~ (0 \le a_{ij} \le 10^9)$.

翻译中…

The following line contains two integers $r$ and $c$ $(1 \le r \le n, 1 \le c \le m)$ — the index of row and the index of column where the chip is now.

翻译中…

Output

翻译中…

Print the expected value of Vasya's final score in the format described in the problem statement.

翻译中…

Note

翻译中…

In the first example, Vasya will move his chip exactly once. The expected value of the final score is equal to $\frac{1^2 + 2^2+ 1^2}{3} = 2$.

翻译中…

样例

Input #1
1 4
1 1 2 1
1 3
Output #1
2
InputCopy OutputCopy
Input #2
2 3
1 5 7
2 3 1
1 2
Output #2
665496238
InputCopy OutputCopy
题目信息
题号
1042E
时间限制
3 s
内存限制
256 MB
标签
动态规划
数学
概率论

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。