import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

/**
 * Created by constanzafierro on 13-06-16.
 */
public class Problem507B {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        String[] line = br.readLine().split(" ");
        int r = Integer.parseInt(line[0]);
        int x = Integer.parseInt(line[1]);
        int y = Integer.parseInt(line[2]);
        long xPrime = Integer.parseInt(line[3]);
        long yPrime = Integer.parseInt(line[4]);
        double distance = Math.sqrt(Math.pow((x-xPrime),2) + Math.pow((y-yPrime),2));
        double steps = Math.ceil(distance/(2*r));
        System.out.println((long)steps);
    }
}
