import java.util.Scanner;


public class MainClass {

    
    public static void main(String[] args) {
        
        Scanner scan = new Scanner(System.in);
        long r = scan.nextLong();
        long x1 = scan.nextLong();
        long y1 = scan.nextLong();
        long x2 = scan.nextLong();
        long y2 = scan.nextLong();

        if(x1 == x2 && y1 == y2){
            System.out.println("0");
            return;
        }
        double distance = (double) Math.sqrt((x1-x2) * (x1-x2) + (y1-y2) * (y1-y2)); 
        int n = 1;
        while(distance > 2 * r){
            distance -= 2 *r;
            n++;
        }
        System.out.println(n);
    
    }

}

    