using System;
using System.Linq;
class Program {
    static void Main() {
        int n = int.Parse(Console.ReadLine());
        var a = Console.ReadLine().Split(' ').Select(int.Parse).ToArray();

        int hit = n;
        for (int i = n - 1; 0 <= i; i--) {
            if (a[i] == hit) {
                hit--;
            }
        }
        Console.WriteLine(hit);
    }
}