import java.io.*;
import java.math.BigInteger;
import java.util.*;

public class TaskB {
    public static StringTokenizer tokenizer;
    public static BufferedReader reader;
    public static PrintWriter writer;
    public static void init() {
        reader = new BufferedReader(new InputStreamReader(System.in));
        writer = new PrintWriter(new OutputStreamWriter(System.out));
//        try {
//            reader = new BufferedReader(new InputStreamReader(new FileInputStream("some.in")));
//            writer = new PrintWriter(new OutputStreamWriter(new FileOutputStream("some.out")));
//        } catch (IOException e) {
//            System.out.println(e);
//            System.exit(1);
//        }
    }
    public static void close() {
        try {
            reader.close();
            writer.flush();
            writer.close();
        } catch (IOException e) {
            System.out.println(e);
            System.exit(1);
        }
    }
    public static String nextToken() {
        while (tokenizer == null || !tokenizer.hasMoreTokens()) {
            try {
                tokenizer = new StringTokenizer(reader.readLine());
            } catch (IOException e) {
                System.out.println(e);
                System.exit(1);
            }
        }
        return tokenizer.nextToken();
    }
    public static int nextInt() {
        return Integer.parseInt(nextToken());
    }
    public static long nextLong() {
        return Long.parseLong(nextToken());
    }
    public static double nextDouble() {
        return Double.parseDouble(nextToken());
    }
    public static float nextFloat() {
        return Float.parseFloat(nextToken());
    }
    public static void main(String[] args) {
        init();
        solve();
        close();
    }

    public static void solve() {
        int r = nextInt();
        int x = nextInt();
        int y = nextInt();
        int xx = nextInt();
        int yy = nextInt();
        double dist = Math.sqrt(((double)xx - (double)x) * ((double)xx - (double)x) + ((double)yy - (double)y) * ((double)yy - (double)y));
//        writer.print((double)yy);
        double result = dist / r / 2;
        if ((int)result == result) {
            writer.print((int)result);
        } else {
            writer.print((int)result+1);
        }
    }
}