#include <iostream>
#include <vector>
using namespace std;

int main()
{
	int n, k, i = 0, f = -1, j = 1;
	cin >> n >> k;
	vector<int>list(n, 0);
	for (int i = 0; i < n; i++)
	{
		cin >> list[i];
	}

	while (i < n and f == -1)
	{
		j = 1;
		while (j + i < n and j <= k and list[i + j] <= list[i])
			j++;
		if (j == k + 1)
			f = i + 1;
		else
			i = i + j;
	}

	cout << f;
}