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

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

long long n, i, k, a[5000001];
long long s = 0;
deque<int> d;

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

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

        while (!d.empty() && d.front() < i - k + 1)
            d.pop_front();

        while (!d.empty() && a[d.back()] >= a[i])
            d.pop_back();

        d.push_back(i);

        if (i >= k)
            s += a[d.front()];
    }

    cout << s;

    return 0;
}