
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		int r,x,y,x1,y1;
		Scanner input=new Scanner(System.in);
		while(input.hasNext())
		{
			r=input.nextInt();
			r<<=1;
			x=input.nextInt();
			y=input.nextInt();
			x1=input.nextInt();
			y1=input.nextInt();
			double dis=Math.sqrt((x1-x)*(x1-x)+(y1-y)*(y1-y));
			//System.out.println(dis);
			if(dis==0)
				System.out.println("0");
			else if(dis<r)
				System.out.println("2");
			else
			{
				int i=1;		
				while(dis-r*i>1e-5)
				{
					++i;
					
				}
				System.out.println(i);
			}
	
		}
	}

}
