import java.util.*;
import java.io.*;

public class Q11 {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner s = new Scanner(System.in);
		long r = s.nextInt();
		long x = s.nextInt();
		long y = s.nextInt();
		long x1 = s.nextInt();
		long y1 = s.nextInt();
		long d = 2 * r;
		long dx = Math.abs(x - x1);
		long dy = Math.abs(y - y1);
		dx *= dx;
		dy *= dy;
		double dist = dx + dy;
		dist = Math.sqrt(dist);
		long ans = (long) dist / d;
		if (dist % d == 0) {
			System.out.println(ans);
		} else {
			System.out.println(ans + 1);
		}
	}

}
