//package Code;
import java.util.*;

import java.math.*;
import java.lang.System;
import java.nio.CharBuffer;
import static java.lang.System.*;
import java.io.InputStream;
import java.sql.Time;

public class Main
{
    public static void main(String[] args)
    {
        Double a, b, c, d, i, j, k, m, n;
        Scanner in = new Scanner(System.in);
        m = in.nextDouble();
        a = in.nextDouble();
        b = in.nextDouble();
        c = in.nextDouble();
        d = in.nextDouble();
        n = Math.sqrt(Math.pow(c - a, 2) + Math.pow(d - b, 2));
        m = m * 2.0;
        System.out.println((int)Math.ceil(n/m));
    }
}