#include <bits/stdc++.h>
using namespace std;
using ll = long long;
// const ll MOD = 1e9+7;

#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()

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

    int n,k; cin >> n >> k;
    vector<int> bal(n), jobb(n), a(n);
    priority_queue<pair<int, int>> q;
    for (int i = 0; i < n; i++) {
    	cin >> a[i];
    	q.push({a[i], i});
    	while (i-q.top().second > k) q.pop();
    	bal[i] = q.top().first;
    }
    
    q = priority_queue<pair<int, int>>();
    for (int i = n-1; i >= 0; i--) {
    	q.push({a[i], i});
    	while (q.top().second-i > k) q.pop();
    	jobb[i] = q.top().first;
    }
    
    for (int i = 0; i < n; i++) {
    	if (bal[i] <= a[i] && jobb[i] <= a[i]) {
    		cout << i+1 << "\n"; return 0;
    	}
    }
    cout << "-1\n";

    return 0;
}