import java.io.*;

/**
 * Created by ahmed on 2/13/2016.
 */
public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader input = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter output = new BufferedWriter(new OutputStreamWriter(System.out));
        String[] line = input.readLine().split(" ");
        int r = Integer.parseInt(line[0]);
        int x = Integer.parseInt(line[1]);
        int y = Integer.parseInt(line[2]);
        int xn = Integer.parseInt(line[3]);
        int yn = Integer.parseInt(line[4]);
        float distance = (float) Math.sqrt((Math.pow(Math.abs(x - xn), 2) + Math.pow(Math.abs(y - yn), 2)));
        int ans = (int) (distance / (2 * r));
        if(distance % (2 * r) != 0) {
            ans ++;
        }
        if(distance < r && distance != 0) {
            ans ++;
        }
        output.write("" + ans);
        output.flush();
    }
}
