using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.IO;

class Iroha
{
    public Iroha() { }
    public static int Main()
    {
        new Iroha().calc();
        return 0;
    }

    Scanner cin;
    
    void calc()
    {
        cin = new Scanner();
        int N = cin.nextInt();
        int[] a = new int[N];
        for (int i = 0; i < N; i++)
        {
            a[i] = cin.nextInt();
        }

        int count = 0;
        for (int i = N - 1; i >= 0; i--)
        {
            if (a[i] == N - count) count++;
        }
        Console.WriteLine(N - count);
    }
}

class Scanner
{
    string[] s;
    int i;

    char[] cs = new char[] { ' ' };

    public Scanner()
    {
        s = new string[0];
        i = 0;
    }

    public string next()
    {
        if (i < s.Length) return s[i++];
        string st = Console.ReadLine();
        while (st == "") st = Console.ReadLine();
        s = st.Split(cs, StringSplitOptions.RemoveEmptyEntries);
        i = 0;
        return next();
    }

    public int nextInt()
    {
        return int.Parse(next());
    }

    public long nextLong()
    {
        return long.Parse(next());
    }

    public double nextDouble()
    {
        return double.Parse(next());
    }

}