import java.util.*;

public class A {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        StringBuilder sb = new StringBuilder();

        double r = sc.nextInt();

        double x = sc.nextInt();
        double y = sc.nextInt();
        double nx = sc.nextInt();
        double ny = sc.nextInt();

        double distance = Math.sqrt(Math.pow(Math.abs(x - nx), 2) + Math.pow(Math.abs(y - ny), 2));

        int ans = (int) Math.ceil((distance) / (2 * r));

        System.out.println(ans);
    }
}