#include <iostream>
#include <vector>
#include <string>
#include <map>
#include <set>
#include <algorithm>
#include <cmath>
#include <queue>
#include <stack>
#include <climits>
using namespace std;

using ll = long long;
const int MOD = 1e9 + 7;

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

    int n, k;
    cin >> n >> k;
    vector<int> nums(n);
    for(int i = 0; i < n; i++) {
        cin >> nums[i];
    }

    vector<bool> can_prefix(n, 0);
    deque<int> dq;
    for(int i = 0; i < n; i++) {
        if(dq.empty()) can_prefix[i] = 1;
        else if(nums[dq.front()] <= nums[i]) can_prefix[i] = 1;
        while(!dq.empty() && nums[dq.back()] <= nums[i]) {
            dq.pop_back();
        }
        dq.push_back(i);
        if(dq.front() < i - k) {
            dq.pop_front();
        }
    }
    vector<bool> can_suffix(n, 0);
    dq.clear();
    for(int i = n-1; i >= 0; i--) {
        if(dq.empty()) can_suffix[i] = 1;
        else if(nums[dq.back()] <= nums[i]) can_suffix[i] = 1;
        while(!dq.empty() && nums[dq.front()] < nums[i]) {
            dq.pop_front();
        }
        dq.push_front(i);
        if(dq.back() >= i + k) {
            dq.pop_back();
        }
    }
    bool can = 0;
    for(int i = 0; i < n; i++) {
        if(can_prefix[i] && can_suffix[i]) {
            cout << i+1 << "\n";
            can = 1;
            break;
        }
    }
    if(!can) cout << "-1\n";
}