import java.util.*;
import java.lang.*;
public class Main {

    public static void main(String args[]) {
        Scanner sc = new Scanner(System.in);
        int[] arr= new int[5];
        for(int i=0; i<5; i++){
            arr[i]=sc.nextInt();
        }
         double d= Math.sqrt((arr[1]-arr[3])*(arr[1]-arr[3])+(arr[2]-arr[4])*(arr[2]-arr[4]));
        if(d/(2*arr[0])%1==0)System.out.println((int)d/(2*arr[0]));
        else System.out.println((int)d/(2*arr[0])+1);
    }
}