import java.io.*;
import java.util.*;
import java.lang.*;

public class Rextester{
    static double distance(int x1,int y1,int x2,int y2){
        return Math.sqrt(Math.pow(x1-x2,2)+Math.pow(y1-y2,2));
    }
    public static void main(String[] args)throws IOException{
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer(br.readLine());
        br.close();
        int r = new Integer(st.nextToken());
        int a = new Integer(st.nextToken());
        int b = new Integer(st.nextToken());
        int x = new Integer(st.nextToken());
        int y = new Integer(st.nextToken());
        int answer=0;
        answer+=distance(a,b,x,y)/(2*r);
        if(distance(a,b,x,y)-(answer*2*r)>0){
            answer++;
        }
        System.out.println(answer);
    }
}