import java.util.Scanner;
import java.util.ArrayList;
import java.util.Arrays;
//import java.util.Collections;
public class QuickStart {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        long r = sc.nextLong();
        long x = sc.nextLong();
        long y = sc.nextLong();
        long x2 = sc.nextLong();
        long y2 = sc.nextLong();
        
        long dist = (long)Math.sqrt((double)x2*x2 + y2*y2);

        int steps = 0;
        if(x == x2 && y == y2){
            System.out.println(steps);
            return;
        }

        while(dist > 0){
            steps++;
            dist-= 2*r;
        }

        System.out.println(steps);
    }
}
	   	   		   				 		  	 					 	