#include <bits/stdc++.h>
using namespace std;

int a[5000005];

int main()
{
    int n, k;
    cin >> n >> k;

    for (int i = 1; i <= n; ++i)
        cin >> a[i];

    deque<int> q;
    int sum = 0;
    for (int i = 1; i <= n; ++i)
    {
        while (!q.empty() && a[i] <= a[q.back()])
            q.pop_back();

        q.push_back(i);

        if (i-k == q.front()) q.pop_front();

        if (i >= k)
            sum += a[q.front()];
    }

    cout << sum;

    return 0;
}