using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace YukiCoder
{
    class Program
    {
        static void Main(string[] args)
        {
            var va = Console.ReadLine().Split().Select(int.Parse)
                    .TakeWhile((d, i) => d == i + 1);
            Console.WriteLine(va.Count() + 1);
            Console.ReadLine();
        }
    }
}