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;
        //int ans=(int) Math.ceil(q);
        //int ans1=(int) Math.floor(q);
     double k=(double) r;
     double sol;
     if(q<k&&q!=0.0)
         sol=2.0;
     else if(q%(2.0*k)==0.0)
         sol=q/(2.0*k);
     else 
     {
         sol=q/(2.0*k);
         sol+=1.0;
         
     }
     long ans;
     ans=(long) sol;
     
        System.out.println(ans);
    }
}