import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.Scanner;


public class B287 {

	public static void main(String[] args) {
		Scanner in=new Scanner(new InputStreamReader(System.in));
		long r=2*in.nextLong();
		long x=in.nextLong();
		long y=in.nextLong();
		long xx=in.nextLong();
		long yy=in.nextLong();
		double dist= (x-xx)*(x-xx);
		dist+=(y-yy)*(y-yy);
		dist=Math.sqrt(dist);
		
		long steps=(int)dist/r;
		if(dist%r!=0)steps++;
		System.out.println(steps);
		
		

	}

}
