import java.util.*;
import java.io.*;
import java.lang.*;
import java.math.*;
public class B {
    public static void main(String[] args) throws Exception {
        BufferedReader bf = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer(bf.readLine());
        int r = Integer.parseInt(st.nextToken());
        int x = Integer.parseInt(st.nextToken());
        int y = Integer.parseInt(st.nextToken());
        int x1 = Integer.parseInt(st.nextToken());
        int y1 = Integer.parseInt(st.nextToken());
        double val = Math.sqrt(1L*(x1 - x)*(x1-x) +  1L*(y1 - y)*(y1-y));
        System.out.println((int)Math.ceil(val/(2*r)));
        // Scanner scan = new Scanner(System.in);
        // PrintWriter out = new PrintWriter(new OutputStreamWriter(System.out)); 
        // int n = Integer.parseInt(bf.readLine());
        // StringTokenizer st = new StringTokenizer(bf.readLine());
        // int[] a = new int[n]; for(int i=0; i<n; i++) a[i] = Integer.parseInt(st.nextToken());
        // int n = Integer.parseInt(st.nextToken());
        // int n = scan.nextInt();
        
        // out.close(); System.exit(0);
    }
}
