#include <iostream>

using namespace std;

int n,k;
int fa[1000000];

int ellenorzes(int i)
{
    for (int j=1;j<=k;j++)
    {
        if (fa[i+j] > fa[i]) return j;
    }
    for (int j=1;j<=k;j++)
    {
        if (fa[i-j] > fa[i]) return j;
    }
    return 0;
}


int main()
{
    cin >> n;
    cin >> k;
    for (int i=0;i<n;i++)
    {
        cin >> fa[i];
    }

    int i=0;
    while (i < n)
    {
        if(ellenorzes(i) == 0) {
            cout << i+1;
            return 0;
        } else i+=ellenorzes(i);
    }
    cout << "-1";

    return 0;
}