// Stop the noise and stop the clocks
// Problem: J. Yet Another Mex Problem
// Contest: Codeforces - MEX Foundation Contest (supported by AIM Tech)
// URL: https://codeforces.com/gym/102412/problem/J
// Time: 2024-01-22 20:28:59
// Memory Limit: 512 MB
// Author: Cocoly1990
// Time Limit: 4000 ms
// 
// Powered by CP Editor (https://cpeditor.org)

#pragma GCC optimize("Ofast","inline","-ffast-math")
#pragma GCC target("avx,sse2,sse3,sse4,mmx")
#include<bits/stdc++.h>
using namespace std;
using i64 = long long;
const int N = 2e5 + 7, SEG_SIZE = N * 100;
const i64 inf = 0x3f3f3f3f3f3f3f3f;

struct Line {
	i64 k, b;
	
	Line (i64 k = 0, i64 b = -inf) : k (k), b (b) {}
	
	i64 val (i64 x) {
		return 1ll * k * x + b;
	}
} info[SEG_SIZE];

struct Node {
	int cnt = 0, L[SEG_SIZE], R[SEG_SIZE];
	
	void insert (int &p, i64 l, i64 r, Line g) {
		if (! p) {
			p = ++ cnt;
			assert (cnt < SEG_SIZE);
			info[p] = g;
			return void ();
		}
		
		if (l == r) return;
		i64 mid = (l + r) >> 1;
		
		if (info[p].val (mid) < g.val (mid)) swap (info[p], g);
		
		if (g.k > info[p].k) insert (R[p], mid + 1, r, g);
		else insert (L[p], l, mid, g);
	}
	
	i64 query (int p, i64 l, i64 r, i64 x) {
		if (! p or l == r) return info[p].val (x);
		
		i64 res = info[p].val (x);
		i64 mid = (l + r) >> 1;
		
		if (x <= mid) res = max (res, query (L[p], l, mid, x));
		else res = max (res, query (R[p], mid + 1, r, x));
		
		return res;
	}
} t;

struct Seg {
	int rt[N << 2];
	i64 V;
	
	void modify (int p, int l, int r, int x, Line g) {
		t.insert (rt[p], 0, V, g);
		
		if (l == r) {
			assert (l == x);
			return void ();
		}
		
		int mid = (l + r) >> 1;
		if (x <= mid) modify (p << 1, l, mid, x, g);
		else modify (p << 1 | 1, mid + 1, r, x, g);
	}
	
	i64 query (int p, int l, int r, int ql, int qr, i64 x) {
		if (ql <= l and r <= qr) return t.query (rt[p], 0, V, x);
		
		int mid = (l + r) >> 1;
		i64 res = -inf;
		if (ql <= mid) res = max (res, query (p << 1, l, mid, ql, qr, x));
		if (qr > mid) res = max (res, query (p << 1 | 1, mid + 1, r, ql, qr, x));
		
		return res;
	}
} seg1, seg2;

struct Segmex {
	int mn[N << 2];
	
	void modify (int p, int l, int r, int x, int k) {
		if (l == r) {
			assert (l == x);
			mn[p] = k;
			return void ();
		}
		
		int mid = (l + r) >> 1;
		if (x <= mid) modify (p << 1, l, mid, x, k);
		else modify (p << 1 | 1, mid + 1, r, x, k);
		
		mn[p] = min (mn[p << 1], mn[p << 1 | 1]);
	}
	
	i64 query (int p, int l, int r, int ql, int qr) {
		if (ql <= l and r <= qr) return mn[p];
		i64 res = inf;
		int mid = (l + r) >> 1;
		if (ql <= mid) res = min (res, query (p << 1, l, mid, ql, qr));
		if (qr > mid) res = min (res, query (p << 1 | 1, mid + 1, r, ql, qr));
		
		return res;
	}
	
	int find (int p, int l, int r, int x) {
		if (l == r) return l;

		int mid = (l + r) >> 1;
		
		if (mn[p << 1] <= x) return find (p << 1, l, mid, x); 
		else return find (p << 1 | 1, mid + 1, r, x);
	}
} segmx;

int n, K, a[N];
i64 sum[N], f[N];

signed main () {
	ios :: sync_with_stdio (false); cin.tie (0); cout.tie (0);
	cin >> n >> K;
	for (int i = 1; i <= n; i ++)
		cin >> a[i], sum[i] = sum[i - 1] + a[i];
	
	seg1.V = n;
	seg2.V = sum[n];
	
	seg1.modify (1, 0, n, 0, Line (0, 0));
	seg2.modify (1, 0, n, 0, Line (0, 0));
	
	for (int i = 1; i <= n; i ++) {
		int l = segmx.query (1, 0, n, 0, a[i]);
		int r = (! a[i]) ? i : segmx.query (1, 0, n, 0, a[i] - 1);
		if (i == 3) cout << l << " " << r << "\n";
		segmx.modify (1, 0, n, a[i], i);
		while (l < r) {
			int v = segmx.find (1, 0, n, r - 1);
			int pos = segmx.query (1, 0, n, 0, v);
			seg2.modify (1, 0, n, pos, Line (v, seg1.query (1, 0, n, pos, r - 1, v)));
			r = pos;
		}	
		
		f[i] = seg2.query (1, 0, n, max (0, i - K), i - 1, sum[i]);
		l = max (0, i - K);
		int v = segmx.find (1, 0, n, l - 1);
		r = (! v) ? i : segmx.query (1, 0, n, 0, v - 1);
		if (l < r) f[i] = max (f[i], 1ll * v * sum[i] + seg1.query (1, 0, n, l, r - 1, v));
		seg1.modify (1, 0, n, i, Line (-sum[i], f[i]));
		seg2.modify (1, 0, n, segmx.query (1, 0, n, 0, 0), Line (0, f[i]));
	}
	
	cout << f[n];
}