import java.io.*;
import java.math.BigInteger;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.*;

public class Main {
    public static void main(String[] args) throws IOException {
        InputReader in = new InputReader(System.in);
        FastPrinter out = new FastPrinter(System.out);
        int r = in.nextInt(), x = in.nextInt(), y = in.nextInt(), xx = in
                .nextInt(), yy = in.nextInt(), count = 0;
        double dis = Math.hypot(x - xx, y-yy);
        while(true){
            if(dis/2 > r){
                dis -= 2*r;
                count++;
            }else{
                if(dis != 0)count++;
                break;
            }
        }
        out.println(count);
        out.close();
    }

}

class InputReader {
    public BufferedReader reader;
    public StringTokenizer tokenizer;

    public InputReader(InputStream stream) {
        reader = new BufferedReader(new InputStreamReader(stream), 32768);
        tokenizer = null;
    }

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

    public String nextLine() {
        try {
            return reader.readLine();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            return null;
        }
    }

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

    public long nextLong() {
        return Long.parseLong(next());
    }

    public double nextDouble() {
        return Double.parseDouble(next());
    }

    public BigInteger nextBigInt() {
        return new BigInteger(next());
    }
}

class FastPrinter extends PrintWriter {

    public FastPrinter(OutputStream out) {
        super(out);
    }

    public FastPrinter(Writer out) {
        super(out);
    }

}