import java.util.Scanner;
public class girando_giro {
    
    public static void main(String[] args){
    
        Scanner sc = new Scanner(System.in);
        
        float r = sc.nextInt();
        float x1 = sc.nextInt();
        float y1 = sc.nextInt();
        float x2 = sc.nextInt();
        float y2 = sc.nextInt();
        sc.nextLine();
        
        x2 = (float)Math.pow(Math.abs(x1-x2), 2);
        y2 = (float)Math.pow(Math.abs(y1-y2), 2);
        
        float dist = (float)Math.sqrt(x2+y2);
        
        int aux = (int)Math.ceil(dist/r);
        
        if(aux%2 != 0)
            aux++;
        
        System.out.println(aux/2);
        
    }
    
}

 	 	   	  			 	   	  		 		 				