import java.util.*;
import java.io.*;

public class x {
	static public void main(String[] args) throws Exception {
		new x().run();
	}
	public void run() throws Exception {
		BufferedReader in = new BufferedReader(
		  new InputStreamReader(System.in));
		
		long t = System.currentTimeMillis();
		in.readLine();
		in.readLine();
		System.out.println((System.currentTimeMillis()-t) * 1e-3);
	}
}