#include <iostream>

using namespace std;

int main()
{
    int N, K, db=0, sorsz=1, x, elso;
    bool boldog=false;
    cin >> N >> K;
    cin >> elso;
    for (int i=2; i<=N && !boldog; i++)
    {
        cin >> x;
        if (x>elso)
        {
            db=0;
            elso=x;
            sorsz=i;
            //cout << sorsz << endl;
        }
        else db++;
        //cout << db << endl;
        if (db==K || sorsz==N) boldog=true;
    }
    if (boldog) {cout << sorsz;}
    else cout << -1;
    return 0;
}