using System;
using System.Linq;
using System.Text.RegularExpressions;

namespace MyCompiler 
{
    class Program 
    {
        public static void Main(string[] args) 
        {
            Console.WriteLine(findNumber(new int[]{ -2, 6, 4, 5, 7, -1, 7, 1, 3, 6, 6, -2, 9, 10, 2, 2}));
        }
        
        public static int findNumber(int[] arr)
        {
            arr = arr.Where(x => x >= 0).ToArray();
            Array.Sort(arr);
            int Min = arr.Min();
            while((arr.Contains(Min)))
            {
                Min++;
            }
            return Min;
            
        }
    }
}