import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.Arrays;

/**
 * <a href="http://codeforces.com/contest/507/problem/B">507B</a>
 */
public class _507B {
    public static void main(String[] args) throws Exception {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        int[] a = convert(reader.readLine());
        int r = a[0];
        double d = d(a[1], a[2], a[3], a[4]);
        System.out.println((int) Math.ceil(d / (2 * r)));
    }

    private static int[] convert(String s) {
        return Arrays.stream(s.split(" ")).mapToInt(Integer::valueOf).toArray();
    }

    private static double d(int x1, int y1, int x2, int y2) {
        return Math.sqrt(Math.pow((x1 - x2), 2) + Math.pow(y1 - y2, 2));
    }
}