import java.util.Scanner; 

public class Temp2
{
	public static void main(String[] args) {
		
		Scanner obj = new Scanner(System.in);
		
		int r = obj.nextInt();
		int x = obj.nextInt();
		int y = obj.nextInt();
		int x1 = obj.nextInt();
		int y1 = obj.nextInt();
		
		double dist = Math.sqrt( Math.pow( (x-x1), 2) + Math.pow( (y-y1), 2) );
		
		int ans;
		if(dist == 0)
		{
			ans = 0;
		}
		else if(dist <= 2*r)
		{
			ans = 1;
		}
		else if(dist%(2*r)==0)
		{
			ans = (int) dist/(2*r);
		}
		else
		{
			ans = (int) dist/(2*r) + 1 ;
		}
		
		System.out.println(ans);
		
	}
}