import java.util.Arrays;
import java.util.Scanner;

public class B {

    void run(){
        Scanner sc = new Scanner(System.in);
        long r = sc.nextLong(), x = sc.nextLong(), y = sc.nextLong(), x2 = sc.nextLong(), y2 = sc.nextLong();
        double D = Math.sqrt((x-x2)*(x-x2) + (y-y2)*(y-y2));
        System.out.println((int)Math.ceil((D)/(2*r)));
    }
    
    void debug(Object...o){
        System.out.println(Arrays.deepToString(o));
    }
    
    public static void main(String[] args) {
        new B().run();
    }
}