import java.io.*;

/**
 * Created on 1/23/15.
 *
 * @author Mike Sorokin
 */
public class B {
    private static final StreamTokenizer in;
    private static final PrintWriter out;
    private static final boolean STDIO = true;

    static {
        if (STDIO) {
            in = new StreamTokenizer(new BufferedReader(new InputStreamReader(System.in)));
            out = new PrintWriter(System.out);
        } else {
            StreamTokenizer tmpIn = null;
            PrintWriter tmpOut = null;
            try {
                tmpIn = new StreamTokenizer(new BufferedReader(new FileReader("input.txt")));
                tmpOut = new PrintWriter(new BufferedWriter(new FileWriter("output.txt")));
            } catch (IOException e) {
                e.printStackTrace();
            }
            in = tmpIn;
            out = tmpOut;
        }
    }

    private static int nextInt() throws IOException {
        in.nextToken();
        return (int) in.nval;
    }

    private static long nextLong() throws IOException {
        in.nextToken();
        return (long) in.nval;
    }

    private static double nextDouble() throws IOException {
        in.nextToken();
        return in.nval;
    }

    private static String next() throws IOException {
        in.nextToken();
        return in.sval;
    }

    public static void main(String[] args) throws IOException {
        int d = 2 * nextInt();
        int x = nextInt();
        int y = nextInt();
        int dx = x - nextInt();
        int dy = y - nextInt();
        double dist = Math.hypot(dx, dy);
        int step = (int) (dist / d);
        if (dist % d > 1e-9) {
            step++;
        }
        out.printf("%d\n", step);
        
        out.close();
    }
}
