import java.util.*;
import java.io.*;
import java.lang.*;
public class Main {
    public static void main(String args[] ) {
        Scanner scan = new Scanner(System.in);
        int r = scan.nextInt();
        int x1 = scan.nextInt();
        int y1 = scan.nextInt();
        int x2 = scan.nextInt();
        int y2 = scan.nextInt();
        double d =Math.sqrt((x1-x2)*(x1-x2) + (y1-y2)*(y1-y2));
        double f = Math.ceil(d);
        int a = (int)Math.ceil(f/(r+r));
        System.out.println(a);
        
    }
}
