#include <iostream>
#include <vector>

using namespace std;

int main()
{
    int n, k;
    cin>>n>>k;
    vector <int> mfa(n+1);
    for (int i=1;i<=n;i++)
    {
        cin >> mfa[i];
    }
    int hatar;
    int i=1;
    int j;
    while (i<=n)
    {
        hatar=(n<i+k ? n : i+k);
        j=i+1;
        while (j<=hatar && mfa[i]>=mfa[j])
        {
            j++;
        }
        if (j>hatar)
        {
            cout<<i;
            return 0;
        }
        i=j;
    }
    cout<<-1;
    return 0;
}