#include <iostream>
#include <deque>
using namespace std;

typedef long long ll;

const int N = 1e5 + 10;
ll n, k, s[N], dp[N];

deque <int> q;

int main()
{
	cin >> n >> k;
	for (int i = 1; i <= n; ++i) 
	{
		cin >> s[i];
		s[i] += s[i-1];
	}
	for (int i = 0; i <= n; ++i)
	{
		if (q.size() && i - q.front() > k) q.pop_front();
		if (i <= k) dp[i] = s[i];
		else if (q.size()) dp[i] = s[i] + dp[q.front() - 1] - s[q.front()];
		while (q.size() && dp[q.back() - 1] - s[q.back()] <= dp[i - 1] - s[i]) q.pop_back();
		q.push_back(i);
	}
	cout << dp[n];
}