import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.stream.Stream;

public class Main {
	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

		//入力値読み込み
		int count = Integer.parseInt(br.readLine());
		int[] num = Stream.of(br.readLine().split(" ")).mapToInt(n -> Integer.parseInt(n)).toArray();

		System.out.println((count % 2 == 0) ? (num[count / 2 - 1] + num[count / 2]) / 2.0 : num[count / 2]);
	}
}