import java.util.*;
import java.io.*;

public class Main {

    public static void main(String[] args) {
        new Main().start();
    }
    
    void start(){
        Scanner reader = new Scanner(System.in);
        int r , counter =0 ;
        int x1,y1,x2,y2 ;
        double d ;
        
        while(reader.hasNext()){
            r = reader.nextInt();
            x1= reader.nextInt();
            y1= reader.nextInt();
            x2= reader.nextInt();
            counter = 0 ;
            y2= reader.nextInt();
            
            d = Math.sqrt( (x2-x1)*(x2-x1) + (y2-y1)*(y2-y1) );
            
            while(d>0){
                d= d- (r*2) ;
                counter ++ ;
            }
            System.out.println(counter);
        }

        
        
        
    }

}
