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

#define int long long

signed main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);

    int n, k;
    cin >> n >> k;
    vector<int> a(n+1);

    for(int i = 1; i <= n; i++) {
        cin >> a[i];
    }
    priority_queue<pair<int, int> > pq;

    for(int i = 1; i <= min(n, k); i++) {
        pq.push({a[i], i});
    }

    for(int i = 1; i <= n; i++) {
        while(pq.top().second < i-k) {
            pq.pop();
        }
        if(i+k <= n) pq.push({a[i+k], i+k});

        if(pq.top().first == a[i]) {
            cout << i << endl;
            return 0;
        }

    }

    cout << -1 << '\n';

}