import java.util.*;
public class AmrPins {
	public static void main(String args[]){
		Scanner s=new Scanner(System.in);
		int r=s.nextInt();
		int x=s.nextInt();
		int y=s.nextInt();
		int x1=s.nextInt();
		int y1=s.nextInt();
		double d=Math.sqrt((x1-x)*(x1-x)+(y1-y)*(y1-y));
		if(d%(2*r)==0)
			System.out.println((int)(d/(2*r)));
		else
			System.out.println((int)(d/(2*r)+1));
	}

}
