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

public class SolveContest {
    private BufferedReader in;
    private PrintWriter out;

    public SolveContest() {
        try {
            in = new BufferedReader(new FileReader("input.txt"));
            out = new PrintWriter(new FileWriter("output.txt"),true);
            solve();
        } catch (Exception e) {
            e.printStackTrace();
            in = new BufferedReader(new InputStreamReader(System.in));
            out = new PrintWriter(System.out);
            solve();
        } finally {
            try {
                in.close();
            } catch (IOException e) {

            }
            out.close();
        }
    }
    StringTokenizer st;
    String nextToken() {
        while (st == null || !st.hasMoreTokens())
            try {
                st = new StringTokenizer(in.readLine());
            } catch (IOException e) {

            }
        return st.nextToken();
    }

    int nextInt() {
        return Integer.valueOf(nextToken());
    }
    long nextLong() {
        return Long.valueOf(nextToken());
    }

    public void solve() {
        int r = nextInt();
        int x1 = nextInt();
        int y1 = nextInt();
        int x2 = nextInt();
        int y2 = nextInt();
        out.print((int)Math.ceil(Math.sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2))/(2*r)));
    }

    public static void main(String[] args) {
        new SolveContest();
    }
}