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

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

class TaskB {
    public void solve(int testNumber, FastScanner in, PrintWriter out) {
        int r = in.nextInt();
        int x1 = in.nextInt();
        int y1 = in.nextInt();
        int x2 = in.nextInt();
        int y2 = in.nextInt();
        
        double dist = Math.sqrt(sq(y2-y1) + sq(x2-x1));

        int res = (int)(dist / (2*r));
        if(dist > res*2*r) ++res;
        out.println(res);
    }

    private long sq(long i) {
        return i*i;
    }
}

class FastScanner {
    BufferedReader br;
    StringTokenizer st;

    public FastScanner(InputStream stream) {
        br = new BufferedReader(new InputStreamReader(stream));
    }

    public String nextToken() {
        while (st == null || !st.hasMoreElements()) {
            try {
                st = new StringTokenizer(br.readLine());
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return st.nextToken();
    }

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

}

