import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.IOException;
import java.lang.Math;
public class January2 {
    public static void main(String[] args) throws IOException{
         BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        String brr[]=br.readLine().trim().split(" ");
        int r=Integer.parseInt(brr[0]);
        int x1=Integer.parseInt(brr[1]);
        int y1=Integer.parseInt(brr[2]);
        int x2=Integer.parseInt(brr[3]);
        int y2=Integer.parseInt(brr[4]);
        long dist=(x1-x2)*(x1-x2)+(y1-y2)*(y1-y2);
        double p=(double) dist;
        double q=Math.sqrt(p);
        int z;
        long sol=0;
        int ans=(int) Math.ceil(q);
        int ans1=(int) Math.floor(q);
        //System.out.println(ans+" "+ans1);
            sol+=(ans/(2*r));
            
            z=(int)(ans%(2*r));
          //  System.out.println(z);
            if(ans<(r)&&ans!=0)
                sol=2;
            
            else if(z!=0)
                sol+=1;
        
        System.out.println(sol);
    }
}