
import java.awt.Point;
import java.util.Arrays;
import java.util.Scanner;

/*
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 */
/**
 *
 * @author btx
 */
public class a {

    public static void main(String[] args) {
	Scanner in = new Scanner(System.in);
	int r = in.nextInt();
	int x = in.nextInt();
	int y = in.nextInt();
	int xj = in.nextInt();
	int yj = in.nextInt();
	Point p = new Point(x, y);
	Point pj = new Point(xj, yj);
	double dist = p.distance(pj);
	if(dist == 0)
	    System.out.println(0);
//	else if(dist <= r)
//	    System.out.println(1);
	else {
	   // dist-=r;
	    dist/=2*r;
	    System.out.println((int)(Math.ceil(dist)));
	    
	}
    }

    

}
