swagnik-and-circles
Source: hackerearth
Difficulty: EASY

Swagnik loves Geometry. One day he came up with a very interesting problem.

Swagnik 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 Swagnik 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 Swagnik to achieve his goal in minimum number of steps.

Input

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.

Output

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

SAMPLE INPUT
2 0 0 0 4

SAMPLE OUTPUT
1

Explanation

Note

In the  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).