/*
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//package codeforces;

import java.util.*;

/**
 *
 * @author Pankaj Birat
 */
public class Amr_and_Pins {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        long r = scan.nextLong();
        long x = scan.nextLong();
        long y =  scan.nextLong();
        long x1 = scan.nextLong();
        long y1 = scan.nextLong();
        double d = Math.sqrt((x1-x)*(x1-x)+(y1-y)*(y1-y));
        //System.out.println("d = " + ((x1-x)*(x1-x)+(y1-y)*(y1-y)));
        double ans = d / (2*r);
        int a = (int)Math.ceil(ans);
        System.out.println(a);
    }
}
