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

public class Solution_B {
    public static void main(String[] args) throws Exception {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        String[] strings = reader.readLine().split(" ");
        int r = Integer.parseInt(strings[0]);
        int x1 = Integer.parseInt(strings[1]);
        int y1 = Integer.parseInt(strings[2]);
        int x2 = Integer.parseInt(strings[3]);
        int y2 = Integer.parseInt(strings[4]);

        double dres = Math.sqrt((x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1)) / (2 * r);
        int res = (int) dres;
        if ((dres - res) > 0) res++;

        System.out.println( res );
    }
}
