using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace racshalo
{
    class Program
    {
        static void Main(string[] args)
        {
            int[] inp = Console.ReadLine().Split().Select(int.Parse).ToArray();
            int fsz = inp[0];
            int max = inp[1];
            int[] fakbeta = Console.ReadLine().Split().Select(int.Parse).ToArray();
            int[] fak = new int[fsz + 2 * max];
            fakbeta.CopyTo(fak, max);
            int u = -1;
            for (int i = max; i < fsz + max; i++)
            {
                if (fak.ToList().GetRange(i - max, 2 * max + 1).Max() <= fak[i])
                {
                    u = i - 2;
                    break;
                }
            }
            Console.WriteLine(u);
            Console.ReadLine();
        }
    }
}