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

namespace benzin
{
    class Program
    {
        static void Main(string[] args)
        {
            string[] be = Console.ReadLine().Split();

            int szam = int.Parse(be[0]);
            int lato = int.Parse(be[1]);

            int[] fak = new int[szam + 2*lato];

            be = Console.ReadLine().Split();

            for (int i = 0; i < be.Length; i++)
            {
                fak[i + lato] = int.Parse(be[i]);
            }

            int temp = 0;

            for (int i = lato; i < szam + lato; i++)
            {
                temp = 0;
                for (int j = lato*-1; j < lato + 1; j++)
                {
                    if (fak[i + j] > fak[i])
                    {
                        break;
                    }
                    else
                    {
                        temp++;
                    }
                }

                if (temp == 2 * lato + 1)
                {
                    Console.WriteLine(i - lato + 1);
                    break;
                }


            }

            if (temp != 2 * lato + 1)
            {
                Console.WriteLine(-1);

            }
            Console.ReadKey();
        }
    }
}