Problem 2953 --5.5.1 Picture

2953: 5.5.1 Picture

正确率: $0.00\%$ 下一题

Time Limit	$1$ 秒/Second(s)	Memory Limit	$512$ 兆字节/Megabyte(s)
提交总数	$0$	正确数量	$0$
裁判形式	标准裁判/Standard Judge	我的状态	尚未尝试
难度		分类标签	usaco

Description

A number, N (1 <= N < 5000), of rectangular posters, photographs and other pictures of the same shape are pasted on a wall. Their sides are all vertical or horizontal. Each rectangle can be partially or totally covered by the others. The length of the boundary of the union of all rectangles is called the perimeter. Write a program to calculate the perimeter.

The vertices of all rectangles have integer coordinates. All coordinates are in the range [-10000,10000] and any existing rectangle has a positive area. The numeric value of the result fits in a 32-bit signed representation.

Input

Line 1:	N, the number of rectangles pasted on the wall.
Lines 2..N+1	In each of the subsequent lines, one can find the integer coordinates of the lower left vertex and the upper right vertex of each rectangle. The values of those coordinates are given as ordered pairs consisting of an x-coordinate followed by a y-coordinate.

Output

A single line with a non-negative integer which corresponds to the perimeter for the input rectangles.

Sample Input复制

7
-15 0 5 10
-5 8 20 25
15 -4 24 14
0 -6 16 4
2 15 10 22
30 10 36 20
34 0 40 16

Sample Output复制

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