import java.util.*;
import java.io.*;
public class AmrAndPins {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        PrintWriter out = new PrintWriter(System.out);
        int r = sc.nextInt();
        int x = sc.nextInt();
        int y = sc.nextInt();
        int x1 = sc.nextInt();
        int y1 = sc.nextInt();
        int xdiff = Math.abs(x-x1);
        int ydiff = Math.abs(y-y1);
        double dist = Math.pow(xdiff,2)+Math.pow(ydiff,2);
        double root = Math.pow(dist,0.5)/(2*(double)r);
        int ans = (int)Math.ceil(root);
        out.println(ans);
        out.close();
        sc.close();
    }
}