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

public class Solution {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
        String str = br.readLine();
        StringTokenizer st = new StringTokenizer(str, " ");
        int radius = Integer.parseInt(st.nextToken());
        int x1 = Integer.parseInt(st.nextToken());
        int y1 = Integer.parseInt(st.nextToken());
        int x2 = Integer.parseInt(st.nextToken());
        int y2 = Integer.parseInt(st.nextToken());
        double distance = Math.sqrt((long)(x1 - x2) * (x1 - x2) + (long)(y1 - y2) * (y1 - y2));
        int ans = (int) Math.ceil(distance / (2 * radius));
        bw.write(ans + "\n");
        bw.flush();
    }
}

