using System;

using System.Linq;

/*

Inicio: 01:13     

Final:  01:40

Tempo:  00:27

*/

public class Program

{

    public static void Main()

    {

        var A = new[] { 1, 3, 6, 4, 1, 2 };

        if (Solution(A) == 5)

            Console.WriteLine("Acertou!");

        else

            Console.WriteLine("Errou!");

    }

    public static int Solution(int[] A) {

        var numerosPositivos = A.Where(obj => obj > 0).OrderBy(o=>o.ToString()).ToList();

        for(int i = 1; i <= 100000; i++)

        {

            if(!numerosPositivos.Contains(i))

            {

                return i;

            }

        }

        return -1;

    }

}