import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Collections;

public class BUFFER2 {

	public static void main(String[] args) throws NumberFormatException, IOException {
		InputStreamReader ir=new InputStreamReader(System.in);
		BufferedReader br=new BufferedReader(ir);
		//int n=Integer.parseInt(br.readLine());
		String[] s=br.readLine().trim().split(" ");
		int r=Integer.parseInt(s[0]);
		int x=Integer.parseInt(s[1]);
		int y=Integer.parseInt(s[2]);
		int x1=Integer.parseInt(s[3]);
		int y1=Integer.parseInt(s[4]);
		double d=Math.pow((x-x1),2)+ Math.pow((y-y1),2);
		d=Math.sqrt(d);
		
		if(d%(2*r)==0)
			System.out.println((int)d/(2*r));
		else
			System.out.println((int)d/(2*r)+1);
		
		
		

	}
}

