
import java.util.*;

public class AmrAndPins {
    public static void main(String[] args) {
        int radius, x1=0, y1=0, x2=0, y2=0, Step;
        
        Scanner in = new Scanner(System.in);
        radius = in.nextInt();
        x1 = in.nextInt();
        y1 = in.nextInt();
        x2 = in.nextInt();
        y2 = in.nextInt();
                
        
        double distance = (double)Math.sqrt(Math.pow(x1 - x2, 2) + Math.pow(y1 - y2, 2));
        Step = (int)(distance / (2*radius));
        
        if ((distance - Step *(2*radius)) != 0){
            Step ++;
        }
        
        System.out.println(Step);
        
    }    
}
