import java.util.* ;
public class codeforces {
	public static void main(String[] args) {
		Scanner in=new Scanner(System.in);
		int r=in.nextInt();
		int x=in.nextInt();int y=in.nextInt();
		int x1=in.nextInt();int y1=in.nextInt();
		int sum=0;
		double distance=Math.sqrt(Math.pow((x1-x),2)+Math.pow((y1-y),2));
		sum+=(distance/(2*r));
		if(distance%(2*r)!=0)sum++;
		System.out.println(sum);
	}
}
