// package Div2;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Scanner;
import java.util.Stack;

public class Sketch {	
	public static void main(String[] args){
		Scanner input = new Scanner(System.in);
		double r = input.nextDouble();
		double x = input.nextDouble();
		double y = input.nextDouble();
		double xx = input.nextDouble();
		double yy = input.nextDouble();
		input.close();
		
		if(x==xx && y==yy){
			System.out.println(0);
			return;
		}			
				
		double dist = Math.sqrt((x-xx)*(x-xx) + (y-yy)*(y-yy));
		double d2 = (double) 2*r;
		
		System.out.println((int) Math.ceil(dist / d2));
		return;
	}
}
