import java.util.*;

public class AmrPins507B
{
    public static void main(String[] args) 
    {
        // Set up scanner
        Scanner sc = new Scanner(System.in); 
        // System.out.println("Enter r");  
        long r = sc.nextLong();
        // System.out.println("Enter x1");  
        long x1 = sc.nextLong();
        // System.out.println("Enter y1");  
        long y1 = sc.nextLong();
        // System.out.println("Enter x2");  
        long x2 = sc.nextLong();
        // System.out.println("Enter y2");  
        long y2 = sc.nextLong();
        
        double totald = Math.sqrt((x2-x1)*(x2-x1) + (y2-y1)*(y2-y1));
        double times = totald / (r * 2.0);
        
        long roundit = (long)times;
        if (roundit - times == 0)
        {
            System.out.println((long)times);
        }
        else
        {
            System.out.println((long)(times+1));
        }
    }
}
      