#include <bits/stdc++.h>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");

int n, k, x;
long long sum = 0;
deque <int> d, poz;

int main()
{
    f >> n >> k;
    for (int i=1; i<=n; ++i) {
        f >> x;
        while (!d.empty() && d.back() > x) {
            d.pop_back();   poz.pop_back();
        }
        d.push_back (x);   poz.push_back (i);

        while (poz.front() <= i - k) {
            d.pop_front();   poz.pop_front();
        }
        if (i >= k)
            sum += d.front();
    }
    g << sum;
    return 0;
}