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

public class Main {
    
    public void solve() throws IOException {
        int r=nextInt(),
            x0=nextInt(), y0=nextInt(),
            x1=nextInt(), y1=nextInt();
        double dist=Math.sqrt(((double)x1-x0)*(x1-x0)+(y1-y0)*(y1-y0));
        long steps=(long)dist/2/r;
        if (dist%(2*r)!=0) steps++;
        out.println(steps);
                
    }

    public static void main(String[] args) throws IOException {
        new Main().run();
    }

    final String fileIn = "test.in";
    final String fileOut = "output.txt";
    BufferedReader in;
    PrintWriter out;
    StringTokenizer st = new StringTokenizer("");

    private void run() throws IOException {
//      if (new File(fileIn).exists())
//          in = new BufferedReader(new FileReader(fileIn));
//      else {
            in = new BufferedReader(new InputStreamReader(System.in)); // стандартный ввод 
//      }
//      if (new File(fileOut).exists()) {
//          out = new PrintWriter(new FileWriter(fileOut));
//      } else {
            out = new PrintWriter(System.out); // стандартный вывод
//      }
        solve();
        in.close();
        out.close();
    }

    String nextToken() throws IOException {
        while (!st.hasMoreTokens())
            st = new StringTokenizer(in.readLine());
        return st.nextToken();
    }

    int gcd(int a, int b) {
        return (b == 0 ? a : gcd(b, a % b));
    }

    int nextInt() throws IOException {
        return Integer.parseInt(nextToken());
    }

    long nextLong() throws IOException {
        return Long.parseLong(nextToken());
    }

    double nextDouble() throws IOException {
        return Double.parseDouble(nextToken());
    }

    String nextLine() throws IOException {
        st = new StringTokenizer("");
        return in.readLine();
    }

    boolean EOF() throws IOException {
        while (!st.hasMoreTokens()) {
            String s = in.readLine();
            if (s == null)
                return true;
            st = new StringTokenizer(s);
        }
        return false;
    }
}