import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
public class codeforces{
 
    public static int solve(int r,int x1,int y1,int x2,int y2){
       return (int)Math.ceil((Math.sqrt(Math.pow((x2-x1),2)+Math.pow((y2-y1),2)))/(2*r));
    }
 
    public static void main(String[] args) throws IOException {
        InputStreamReader isr=new InputStreamReader(System.in);
        BufferedReader br=new BufferedReader(isr);
        // StringBuilder str=new StringBuilder();
        PrintWriter out=new PrintWriter(System.out);
        // int n=Integer.parseInt(br.readLine());
        String[] lol=br.readLine().split(" ");
        int r=Integer.parseInt(lol[0]);
        int x1=Integer.parseInt(lol[1]);
        int y1=Integer.parseInt(lol[2]);
        int x2=Integer.parseInt(lol[3]);
        int y2=Integer.parseInt(lol[4]);
        out.println(solve(r,x1,y1,x2,y2));
        out.close();
    }
}     