import java.util.*;
import java.io.*;
import java.math.*;
public class Solution {
	
	public static int MOD = 1000000007;
	public static int MAX = 1000002;
	public static void main(String[] args)throws IOException{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		PrintWriter out = new PrintWriter(System.out,true);
		StringTokenizer st = new StringTokenizer(br.readLine());
		int r = Integer.parseInt(st.nextToken()); 
		int x = Integer.parseInt(st.nextToken());
		int y = Integer.parseInt(st.nextToken());
		int x1 = Integer.parseInt(st.nextToken());
		int y1 = Integer.parseInt(st.nextToken());
		double d = Math.sqrt(((x1-x)*(x1-x)*1.0)+((y-y1)*(y-y1)*1.0));
		out.println((int)Math.ceil(d/(2*r)));
	}		

}
