import java.util.*;
public class KnightTemplar {
public static void main(String [] args){
	Scanner in=new Scanner(System.in);
	int r=in.nextInt();
	double x=in.nextInt();
	double y=in.nextInt();
	double x1=in.nextInt();
	double y1=in.nextInt();
	
	double dist=(x1-x)*(x1-x) + (y1-y)*(y1-y);
	dist=Math.sqrt(dist);
	dist=Math.ceil(dist/(2*r));
	System.out.print((int)dist);
}
}
    