import java.util.*;

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

        if (!scanner.hasNextInt()) {
            System.out.println("Invalid input");
            scanner.close();
            return;
        }

        int n = scanner.nextInt();

        // Validate: n should be even, > 0 and ≤ 10
        if (n <= 0 || n > 10 || n % 2 != 0) {
            System.out.println("Invalid input");
            scanner.close();
            return;
        }

        int[] arr = new int[n];

        for (int i = 0; i < n; i++) {
            if (!scanner.hasNextInt()) {
                System.out.println("Invalid input");
                scanner.close();
                return;
            }
            arr[i] = scanner.nextInt();
        }

        int mid = n / 2;

        for (int i = mid - 1, j = mid; i >= 0 && j < n; i--, j++) {
            System.out.println(arr[i] + "," + arr[j]);
        }

        scanner.close();
    }
}