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

public class Main {

    public static void main(String[] args) throws java.lang.Exception {
	java.io.BufferedReader r = new java.io.BufferedReader(new java.io.InputStreamReader (System.in));

	StringTokenizer st = new StringTokenizer(r.readLine());
	double rad = toDouble(st.nextToken());
	double x = toDouble(st.nextToken());
	double y = toDouble(st.nextToken());
	double x1 = toDouble(st.nextToken());
	double y1 = toDouble(st.nextToken());

	double distance = Math.sqrt((y1-y)*(y1-y) + (x1-x)*(x1-x));
	double ans = Math.ceil(distance/(2*rad));
	Double tmp = new Double(ans);
	prnt(tmp.intValue());

    }

    public static void prnt(String s) {
	System.out.println(s);
    }
    public static void prnt(int s) {
	System.out.println(s);
    }
    public static void prnt(double s) {
	System.out.println(s);
    }
    public static void prnt(long s) {
	System.out.println(s);
    }
    public static void prnt(char s) {
	System.out.println(s);
    }
    public static int toInt(String s) {
	return Integer.parseInt(s);
    }
    public static long toLong(String s) {
	return Long.parseLong(s);
    }
    public static double toDouble(String s) {
	return Double.parseDouble(s);
    }
}
