import java.util.Arrays;
import java.util.Scanner;

/**
 * Calcualtes the median of a numbered set of real values
 */
public class Solution
{
	/**
	 * Gets data from standard input
	 */
	private Scanner input;

	/**
	 * Start the execution of the solution
	 * @param args Command line arguments
	 */
	public static void main(String args[])
	{
		Solution solution = new Solution();
		solution.run();
	}

	/**
	 * Run the solution. This method is called from main()
	 */
	public void run()
	{
		// Create object to read data from standard input
		input = new Scanner(System.in);

		// Read the number of elements
		int size = input.nextInt();

		// Create an array to store all the values
		double values[] = new double[size];

		// Read all values
		for ( int index = 0; index < values.length; ++index )
		{
			values[index] = input.nextDouble();
		}

		// Sort all the values
		Arrays.sort(values);

		// The median is the value at the center
		if ( values.length % 2 == 1 )
		{
			// The array has an odd number of elements, we have a value at the center
			System.out.printf("%.2f\n", values[ values.length / 2 ] );
		}
		else
		{
			// We do not have a value at the center, so we calculate the average (mean)
			// of the two values around the center of the array
			double mean = ( values[values.length / 2 - 1] + values[values.length / 2] ) / 2.0;
			System.out.printf("%.2f\n", mean);
		}

		// Close the standard input
		input.close();
	}
}