static void Main(string[] args)
{
int amount = int.Parse(Console.ReadLine());
string[] temp = Console.ReadLine().Split(' ');
List<int> list = new List<int>();
for (int i = 0; i < temp.Length; i++)
{
if (!list.Contains(int.Parse(temp[i])))
list.Add(int.Parse(temp[i]));
}
int[] numbers = list.ToArray();
Array.Sort(numbers);
if (numbers.Length > 1)
Console.WriteLine(numbers[1]);
else
Console.WriteLine("NO");
Console.ReadLine();
}