/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
//package amrandpins;
import java.util.*;
/**
 *
 * @author Rawhi
 */
public class AmrAndPins {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        double r = sc.nextDouble(),x = sc.nextDouble(),y = sc.nextDouble(),xP = sc.nextDouble(),yP = sc.nextDouble();
        int totalSteps = 0;
        double diagonal = Math.sqrt(Math.pow(Math.abs(Math.abs(Math.max(x, xP)) - Math.abs(Math.min(x, xP))),2) + Math.pow(Math.abs(Math.abs(Math.max(y, yP)) - Math.abs(Math.min(y, yP))),2));
        
        while (diagonal > 0) {
            diagonal -= r * 2;
            totalSteps++;
        }
        System.out.println(totalSteps);
    }
    
}
