
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;

public class AmrandPins {
public static void main(String[] args) throws IOException {
	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
	StringTokenizer str  = new StringTokenizer(br.readLine());
	double  r = Integer.parseInt(str.nextToken());
	double  x = Integer.parseInt(str.nextToken());
	double  y = Integer.parseInt(str.nextToken());
	double  xx = Integer.parseInt(str.nextToken());
	double  yy = Integer.parseInt(str.nextToken());
	
	
	double d = Math.sqrt(Math.pow(Math.abs(x-xx), 2)+Math.pow(Math.abs(y-yy), 2));
	
	System.out.println((int)Math.ceil(d/(2*r)));
	
}
}
