import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.StringTokenizer;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        BAmrAndPins solver = new BAmrAndPins();
        solver.solve(1, in, out);
        out.close();
    }

    static class BAmrAndPins {
        public void readInput(Scanner sc) {

        }

        public void solve(int testNumber, Scanner sc, PrintWriter pw) {
            int tc = 1;
            while (tc-- > 0) {
                readInput(sc);
                double r = sc.nextInt();
                int[] source = new int[]{sc.nextInt(), sc.nextInt()}, dist = new int[]{sc.nextInt(), sc.nextInt()};
                int diffX = Math.abs(source[0] - dist[0]), diffY = Math.abs(source[1] - dist[1]);
                double d = Math.sqrt(diffX * diffX + diffY * diffY);
                pw.println((int) Math.ceil(d / (r * 2)));
            }
        }

    }

    static class Scanner {
        StringTokenizer st;
        BufferedReader br;

        public Scanner(InputStream s) {
            br = new BufferedReader(new InputStreamReader(s));
        }

        public String next() {
            try {
                while (st == null || !st.hasMoreTokens())
                    st = new StringTokenizer(br.readLine());
                return st.nextToken();
            } catch (Exception e) {
                throw new RuntimeException(e);
            }
        }

        public int nextInt() {
            return Integer.parseInt(next());
        }

    }
}

