// package question1;

import java.util.Arrays;
import java.util.Scanner;

public class Solution {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        double r =sc.nextDouble();
        double x = sc.nextDouble();
        double y = sc.nextDouble();
        double x1=sc.nextDouble();
        double y1 = sc.nextDouble();
        double ans = Math.sqrt((y1-y)*(y1-y)+(x1-x)*(x1-x));
        double fans =Math.ceil(ans/(2*r));
        System.out.println((int)(fans));
    }
}
