import java.util.*;

public class B {

    public static void main(String[] args) {
    	Scanner s = new Scanner(System.in);
    	int r = s.nextInt();
    	int x = s.nextInt();
    	int y = s.nextInt();
    	int xx = s.nextInt();
    	int yy = s.nextInt();
    	System.out.println((int)Math.ceil(Math.sqrt(Math.pow(x-xx,2)+Math.pow(y-yy,2))/(2*r)));
    }
}
