import java.util.*;
// scanner.nextInt();
public class Solution {
    public static void main(String[] args) {
        
        Scanner scanner = new Scanner(System.in);
        
            
            
                int r = scanner.nextInt();
                int x = scanner.nextInt();
                int y = scanner.nextInt();
                
                int xx = scanner.nextInt();
                int yy = scanner.nextInt();
                
                double d = dist(x, y, xx, yy);
                
                double t = Math.ceil(d/(double)(2*r));
                
                int res = (int)t;
                System.out.println(res);
		//int[] array = new int[n];
                /*

                for(int i = 0; i < n; ++i)
                    {
                        array[i] = scanner.nextInt();
                    }
                 */
                //String[] arr = {"aa","bb","c", "d","ee", "ff" , "gg" , "hh", "ii" , "jj" , "k" , "l", "m", "n", "o", "p", "q" , "r", "s", "t", "u" , "v", "w" ,"x", "y", "z"};
 
            
                    
    }
    
    public static double dist(int x, int y, int xx, int yy)
    {
        return Math.sqrt((x-xx)*(x-xx) + (y-yy)*(y-yy));
    }
}

