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));
		int r=2*in.nextInt();
		int x=in.nextInt();
		int y=in.nextInt();
		int xx=in.nextInt();
		int yy=in.nextInt();
		double dist= Math.sqrt((x-xx)*(x-xx)+(y-yy)*(y-yy));
		int steps=(int)dist/r;
		if(dist%r!=0)steps++;
		System.out.println(steps);
		
		

	}

}
