using System;
using System.Linq;
class Program {
    static void Main() {
        int ans = 0;
        int n = int.Parse(Console.ReadLine());
        var a = Console.ReadLine().Split(' ').Select(int.Parse).ToList();

        for (int i = n; 0 <= i; i--) {
            int ai = a.IndexOf(i);
            for (int j = i - 1; 0 <= j; j--) {
                if (ai < a.IndexOf(j)) {
                    ans = Math.Max(ans, j);
                    break;
                }
            }
        }
        Console.WriteLine(ans);
    }
}