
import java.util.Scanner;

/*
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/**
 *
 * @author KHALED
 */
public class AmrAndPins {
    public static void main(String[] args) {
        Scanner scan=new Scanner(System.in);
        int r=scan.nextInt();
        int x1=scan.nextInt();
        int y1=scan.nextInt();
        int x2=scan.nextInt();
        int y2=scan.nextInt();
        double d=Math.sqrt((x2-x1)*(x2-x1)+(y2-y1)*(y2-y1));
        int out=(int)Math.ceil(d/(2*r));
        System.out.println(out);
    }
}
