#include <bits/stdc++.h>

using namespace std;

ifstream in("deque.in");
ofstream out("deque.out");

int n, k, a[5000005];

int main()
{
    in >> n >> k;
    for (int i = 1; i <= n; i++)
        in >> a[i];
    long long sum = 0;
    deque<int> dq;
    for (int i = 1; i <= n; i++)
    {
        while (!dq.empty() and a[i] <= a[dq.back()])
            dq.pop_back();
        while (!dq.empty() and dq.front() <= i - k)
            dq.pop_front();
        dq.push_back(i);
        if (i >= k)
            sum += a[dq.front()];
    }
    out << sum;
    return 0;
}