AtCoder Beginner Contest 127
E
Cell Distance
AtCoder
⌀ 1938
原题
← DF →
翻译中…

Problem Statement

翻译中…

We have a grid of squares with $N$ rows and $M$ columns. Let $(i, j)$ denote the square at the $i$-th row from the top and $j$-th column from the left. We will choose $K$ of the squares and put a piece on each of them.

翻译中…

If we place the $K$ pieces on squares $(x_1, y_1)$, $(x_2, y_2)$, ..., and $(x_K, y_K)$, the cost of this arrangement is computed as:

翻译中…

$\sum_{i=1}^{K-1} \sum_{j=i+1}^K (|x_i - x_j| + |y_i - y_j|)$

翻译中…

Find the sum of the costs of all possible arrangements of the pieces. Since this value can be tremendous, print it modulo $10^9+7$.

翻译中…

We consider two arrangements of the pieces different if and only if there is a square that contains a piece in one of the arrangements but not in the other.

翻译中…

Constraints

翻译中…
  • $2 \leq N \times M \leq 2 \times 10^5$
  • $2 \leq K \leq N \times M$
  • All values in input are integers.
翻译中…

Input

翻译中…

Input is given from Standard Input in the following format:

翻译中…

N M K

翻译中…

Output

翻译中…

Print the sum of the costs of all possible arrangements of the pieces, modulo $10^9+7$.

翻译中…

样例

Input #1
2 2 2
Output #1
8
There are six possible arrangements of the pieces, as follows: - $((1,1),(1,2))$, with the cost $|1-1|+|1-2| = 1$ - $((1,1),(2,1))$, with the cost $|1-2|+|1-1| = 1$ - $((1,1),(2,2))$, with the cost $|1-2|+|1-2| = 2$ - $((1,2),(2,1))$, with the cost $|1-2|+|2-1| = 2$ - $((1,2),(2,2))$, with the cost $|1-2|+|2-2| = 1$ - $((2,1),(2,2))$, with the cost $|2-2|+|1-2| = 1$ The sum of these costs is $8$.
Input #2
4 5 4
Output #2
87210
Input #3
100 100 5000
Output #3
817260251
Be sure to print the sum modulo $10^9+7$.
题目信息
题号
abc127_e
时间限制
2 s
内存限制
1024 MB

题面与样例版权归 AtCoder 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。