#include <bits/stdc++.h>
//#define ll long long
using namespace std;

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);

    int n,k,x,max=-1,maxi=-2,f=0; cin >> n >> k;
    bool talalt = false;
    for (int i = 0; i < n && !talalt; i++)
    {
        cin >> x;
        if (x > max)
        {
            max = x;
            maxi = i;
            f = 0;
        }
        else
        {
            f++;
        }
        if (f == k)
        {
            talalt = true;
        }
    }

    cout << (talalt ? maxi+1 : -1) << endl;
    return 0;
}