4255：A Famous Grid

题目描述

Mr. B has recently discovered the grid named "spiral grid".
Construct the grid like the following figure. (The grid is actually infinite. The figure is only a small part of it.)

Considering traveling in it, you are free to any cell containing a composite number or 1, but traveling to any cell containing a prime number is disallowed. You can travel up, down, left or right, but not diagonally. Write a program to find the length of the shortest path between pairs of nonprime numbers, or report it's impossible.

输入解释

Each test case is described by a line of input containing two nonprime integer 1 <=x, y<=10,000.

输出解释

For each test case, display its case number followed by the length of the shortest path or "impossible" (without quotes) in one line.

输入样例

1 4
9 32
10 12

输出样例

Case 1: 1
Case 2: 7
Case 3: impossible

来自杭电HDUOJ的附加信息

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该题目是Virtual Judge题目，来自杭电HDUOJ

题目来源 Fudan Local Programming Contest 2012

源链接： HDU-4255

最后修改于 2020-10-25T23:11:47+00:00 由爬虫自动更新

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通过率 --%

时间上限	内存上限
10000/3000MS(Java/Others)	32768/32768K(Java/Others)