import java.util.*;

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

        int n = s.nextInt();   // size of array

        if (n < 2) {
            System.out.println("Invalid input");
            return;
        }

        int arr[] = new int[n];
        for (int i = 0; i < n; i++) {
            arr[i] = sc.nextInt();
        }

        
        Arrays.sort(arr);

        
        if (arr[n-1] == arr[n-2]) {
            System.out.println("Invalid input");
        } else {
            System.out.println(arr[n-2]);
        }
    }
}