public class Program
{
    public static void Main()
    {
        int N = int.Parse(Console.ReadLine()!);
        var p_array = Console.ReadLine()!.Split('\x20').Select(int.Parse);

        var list = new LinkedList<int>();
        var nodes = new LinkedListNode<int>?[N];

        foreach (var n in p_array)
        {
            nodes[n - 1] = list.AddLast(n);
        }

        List<int> q = new(N);

        for (int i = 0; i < N; i++)
        {
            var node0 = nodes[i];
            if (node0 is not null)
            {
                var node1 = node0.Next;

                if (node1 == null)
                {
                    continue;
                }

                nodes[node0.Value - 1] = null;
                q.Add(node0.Value);
                list.Remove(node0);

                nodes[node1.Value - 1] = null;
                q.Add(node1.Value);
                list.Remove(node1);
            }
        }

        foreach (var n in q)
        {
            Console.Write(n);
            Console.Write('\x20');
        }
        Console.Write(Environment.NewLine);
        return;
    }
}