import java.util.Scanner;

public class Array
{
    public static void main(String[] args) 
    {
        Scanner input = new Scanner(System.in);

        double[] num = new double[4];   // Defines an array

        for ( int i = 0; i < 4; i++)
        {
            System.out.print("Enter number " + i + ":");
            num[i] = input.nextDouble(); // i is an index to the array
        }
        
        double sum = 0;
        for ( int i = 0; i < 4; i++)
            sum = sum + num[i];
        System.out.println(sum/4);
    } 
}