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A12854 | Rectangle Painting 2

时间限制1s
内存限制256MB
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题目描述

There is a square grid of size $n \times n$ . Some cells are colored in black, all others are colored in white. In one operation you can select some rectangle and color all its cells in white. It costs $\min(h, w)$ to color a rectangle of size $h \times w$ . You are to make all cells white for minimum total cost.

The square is large, so we give it to you in a compressed way. The set of black cells is the union of $m$ rectangles.

输入格式

The first line contains two integers $n$ and $m$ ( $1 \le n \le 10^{9}$ , $0 \le m \le 50$ ) — the size of the square grid and the number of black rectangles.

Each of the next $m$ lines contains 4 integers $x_{i1}$ $y_{i1}$ $x_{i2}$ $y_{i2}$ ( $1 \le x_{i1} \le x_{i2} \le n$ , $1 \le y_{i1} \le y_{i2} \le n$ ) — the coordinates of the bottom-left and the top-right corner cells of the $i$ -th black rectangle.

The rectangles may intersect.

输出格式

Print a single integer — the minimum total cost of painting the whole square in white.

输入输出样例

输入 #1
10 2
4 1 5 10
1 4 10 5
输出 #1
4
输入 #2
7 6
2 1 2 1
4 2 4 3
2 5 2 5
2 3 5 3
1 2 1 2
3 2 5 3
输出 #2
3
C++ 编辑器
输入
输出