Amr and Pins

题意翻译

给定一个半径为 $r$ 的圆，圆心在 $(x,y)$ 处。每次可以把圆固定在圆内的某点选择任意度数，使圆心移动到 $(x',y')$ 处。求最小旋转次数。

题目描述

Amr loves Geometry. One day he came up with a very interesting problem. Amr has a circle of radius $ r $ and center in point $ (x,y) $ . He wants the circle center to be in new position $ (x',y') $ . In one step Amr can put a pin to the border of the circle in a certain point, then rotate the circle around that pin by any angle and finally remove the pin. Help Amr to achieve his goal in minimum number of steps.

输入输出格式

输入格式

Input consists of 5 space-separated integers $ r $ , $ x $ , $ y $ , $ x' $ $ y' $ ( $ 1<=r<=10^{5} $ , $ -10^{5}<=x,y,x',y'<=10^{5} $ ), circle radius, coordinates of original center of the circle and coordinates of destination center of the circle respectively.

输出格式

Output a single integer — minimum number of steps required to move the center of the circle to the destination point.

输入输出样例

输入样例 #1

2 0 0 0 4

输出样例 #1

1

输入样例 #2

1 1 1 4 4

输出样例 #2

3

输入样例 #3

4 5 6 5 6

输出样例 #3

0

说明

In the first sample test the optimal way is to put a pin at point $ (0,2) $ and rotate the circle by $ 180 $ degrees counter-clockwise (or clockwise, no matter).