import java.io.*;
import java.util.*;

public class cf287B {
    public static void main(String[] args) throws Exception {
    	// BufferedReader in = new BufferedReader(new FileReader("cf287B.in"));
    	BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
    	
		String[] arr = in.readLine().split(" ");
		
		int[] a = new int[arr.length];
		for(int i = 0; i < a.length; i++) {
			a[i] = Integer.parseInt(arr[i]);
		}
		int r = Integer.parseInt(arr[0]);
		int x = Integer.parseInt(arr[1]);
		int y = Integer.parseInt(arr[2]);
		int x1 = Integer.parseInt(arr[3]);
		int y1 = Integer.parseInt(arr[4]);
		long l = (long) (x - x1) * (x - x1) + (long) (y - y1) * (y - y1);
		double d = Math.sqrt(l) / (2 * r);
		System.out.println((int) Math.ceil(d));
	}
}