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

/**
 * Calculates 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
		this.input = new Scanner(System.in);

		// Create an array to store all the values
		DoubleArray values = new DoubleArray();

		// Read all values
		while ( this.input.hasNextDouble() )
		{
			values.append( input.nextDouble() );
		}

		// Sort all the values
		values.bubbleSort();

		// The median is the value at the center
		if ( values.getCount() % 2 == 1 )
		{
			// The array has an odd number of elements, we have a value at the center
			System.out.printf("%.2f\n", values.getAt( values.getCount() / 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 sum = values.getAt(values.getCount() / 2 - 1)
					+ values.getAt(values.getCount() / 2);
			double mean = sum / 2.0;
			System.out.printf("%.2f\n", mean);
		}

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