
import java.util.Scanner;

public final class Circles {
public static void main(String[] args) {
	Scanner sc=new Scanner(System.in);
	double r=sc.nextInt();
	int x1=sc.nextInt();
	int y1=sc.nextInt();
	int x2=sc.nextInt();
	int y2=sc.nextInt();
	if(x1==x2 && y1==y2)
		System.out.println(0);
	else
	{
		double distance=Math.pow(Math.pow(x1-x2, 2)+Math.pow(y1-y2, 2), 0.5);
		System.out.println((int)Math.ceil(distance/(2*r)));
	}
}
}
