import java.util.ArrayList;
import java.util.Scanner;

public class AverageOfNumbers  {

    public static void main(String[] args) {
        Scanner read = new Scanner(System.in);
        ArrayList<Integer> numbers = new ArrayList<>();

        while (true) {
            int number = read.nextInt();

            if (number == 0) {
                break;
            } else {
                numbers.add(number);
            }
        }

        if(numbers.stream().anyMatch(i -> i < 0)){
            System.out.println("Cannot calculate the average");
        } else {
            int sum = numbers.stream().mapToInt(Integer::intValue).sum();
            int count = numbers.size();
            System.out.println(sum / count);
        }
    }
}