import java.util.Scanner;
public class BAmrAndPins { 
    public static void main(String[] args) {
        Scanner x = new Scanner(System.in);
        int r , Pointx1 , Pointx2 , Pointy1 , Pointy2 ;
        
        r = x.nextInt(); 
        Pointx1 = x.nextInt();
        Pointy1 = x.nextInt();
        Pointx2 = x.nextInt();
        Pointy2 = x.nextInt();
        
        r += r;
        double dis = Math.sqrt(Math.pow(Pointx2 - Pointx1, 2) + Math.pow(Pointy2 - Pointy1, 2));
        int diss = (int) dis;
        if (diss != dis) {
            diss++;
        }
        System.out.println(diss % r == 0 ? diss / r : (diss / r) + 1);
    }
    
}
