import java.util.*;

public class helloWorld 
{
	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 xx = in.nextInt();
		int yy = in.nextInt();
		
		long ans = (long)(xx-x)*(xx-x) + (long)(yy-y)*(yy-y);
		ans = (int) Math.ceil( Math.sqrt(ans) / (2*r) );
	
		System.out.print(ans);
		
		in.close();
	}
}