dp

#include <bits/stdc++.h>
using namespace std;
const int N = 1e6 + 1;
int a[N], f[N], n, k, minn = INT_MAX;
struct point {
	point(int v, int i) : val(v), id(i) {}
	int val; int id;
};
deque<point> Q;
void push(int x, int i) {
	while (!Q.empty() && x < Q.back().val) Q.pop_back();
	Q.push_back(point(x, i));
	while (Q.front().id < i - k + 1) Q.pop_front();
}
int main() {
	cin >> n >> k;
	for (int i = 1; i <= n; i ++)
		cin >> a[i];
	for (int i = 1; i <= k; i ++)
		f[i] = a[i], push(f[i], i);
	for (int i = k; i <= n; i ++) {
		if (i >= k) f[i] = Q.front().val + a[i];
		push(f[i], i);
	}
	for (int i = n - k + 1; i <= n; i ++)
		minn = min(minn, f[i]);
	cout << minn << '\n';
	return 0;
}