#include <bits/stdc++.h>


using namespace std;


int main(){



    int n, k; cin >> n >> k;

    bool m = false;

    vector<int> v;

    for (int i = 0; i < n; i++){

        int x; cin >> x; v.push_back(x);


    }

    multiset<int> s;

    for (int i = 0; i < k; i++){
        s.insert(v[i]);
    }

    for (int i = 0; i <= k; i++){
        if (i+k < n) s.insert(v[i+k]);
        if (*s.rbegin() == v[i]){cout << i+1;  m = true; break;}
    }


    if (!m){for (int i = k+1; i < n; i++){
        if (i+k < n) s.insert(v[i+k]);
        s.erase(s.find(i-k));
        if (*s.rbegin() == v[i]){cout << i+1; m = true; break;}
    }}


    if (!m) cout << -1;


    return 0;
}