using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    static int[][] NArr(long n) => Enumerable.Repeat(0, (int)n).Select(_ => NList).ToArray();
    static string[] SList(long n) => Enumerable.Repeat(0, (int)n).Select(_ => ReadLine()).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var n = NN;
        var a = NList;
        var pos = new int[n + 1];
        for (var i = 0; i < n; ++i) pos[a[i]] = i;
        var ans = 0;
        for (var i = 1; i <= n; ++i)
        {
            if (a[pos[i]] > 0)
            {
                ++ans;
                a[pos[i]] = 0;
                if (pos[i] > 0) a[pos[i] - 1] = 0;
            }
        }
        WriteLine(ans);
    }
}