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

public class CircleCenter {
    public static int numberOfSteps(int r, int x, int y, int xx, int yy) {
        long distance = (long) Math.ceil(getDistance(x, y, xx, yy));
        return (int) Math.ceil(distance / (2 * r));
    }

    public static double getDistance(long x, long y, long xx, long yy) {
        return Math.sqrt((xx - x) * (xx - x) + (yy - y) * (yy - y));
    }

    public static void main(String[] args) throws IOException {
        BufferedReader scanner = new BufferedReader(new InputStreamReader(
                System.in));
        StringTokenizer tokenizer = new StringTokenizer(scanner.readLine());
        int r = Integer.parseInt(tokenizer.nextToken());
        int x = Integer.parseInt(tokenizer.nextToken());
        int y = Integer.parseInt(tokenizer.nextToken());
        int xx = Integer.parseInt(tokenizer.nextToken());
        int yy = Integer.parseInt(tokenizer.nextToken());

        System.out.println(numberOfSteps(r, x, y, xx, yy));
    }
}
