#include <bits/stdc++.h> 
using namespace std;  
 
typedef long long ll;  
typedef pair<int, int> ii;  
 
const int INF = 1e9;  
const ll LINF = 1e18;  
 
template<typename T>
bool maximize(T& a, const T& b) {
	if (b < a) return false; 
	a = b; 
	return true; 
}
 
const int N = 1e5 + 5; 
 
int n, k; 
int a[N]; 
 
ll seg[4 * N];  
 
void update(int id, int l, int r, int pos, ll val) {
	if (l > pos || r < pos) return;  
 
	maximize(seg[id], val);   
	if (l == r) return;  
 
	int mid = (l + r) >> 1; 
	update(id * 2, l, mid, pos, val); 
	update(id * 2 + 1, mid + 1, r, pos, val); 
}
 
ll getMax(int id, int l, int r, int u, int v) {
	if (l > v || r < u) return -LINF; 
 
	if (u <= l && r <= v) return seg[id];  
 
	int mid = (l + r) >> 1; 
	return max(getMax(id * 2, l, mid, u, v), getMax(id * 2 + 1, mid + 1, r, u, v)); 
}
 
ll dp[N]; // dp[i] = Số tiền nhiều nhất kiếm được nếu bắt đầu chọn từ hộp thứ i 
 
int main() {
	ios::sync_with_stdio(0); cin.tie(0);  	
	cin >> n >> k; 
	for (int i = 1; i <= n; i++) cin >> a[i]; 
 
	// for (int i = n; i >= 1; i--) {
	// 	dp[i] = a[i];  
	// 	for (int j = i + 1; j <= min(n, i + k); j++) {
	// 		maximize(dp[i], a[i] + dp[j]); 
	// 	} 
	// }
 
	for (int i = n; i >= 1; i--) {
		// chỉ chọn duy nhất hộp i 
		dp[i] = a[i];  
 
		// chọn hộp i cùng một số hộp khác ở phía sau
		maximize(dp[i], a[i] + getMax(1, 1, n, i + 1, min(n, i + k))); 
 
		update(1, 1, n, i, dp[i]); 
	}
 
	ll ans = 0;   
	for (int i = 1; i <= n; i++) maximize(ans, dp[i]); 
 
	cout << ans << '\n'; 
}
 

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NSAyCi0xIC0yIDMgLTQgNQo=

5 2
-1 -2 3 -4 5