#include <bits/stdc++.h>

using namespace std;

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

int v[5000005];

deque < int > dq;

int main()
{
    int n, k, i;
    long long s = 0;

    fin >> n >> k;

    for (i = 1; i <= n; ++i)
        fin >> v[i];

    for (i = 1; i <= n; ++i)
    {
        while (!dq.empty() && v[dq.back()] >= v[i])
        {
            dq.pop_back();
        }
        dq.push_back(i);
        if (dq.front() == i - k)
            dq.pop_front();
        if (i >= k)
            s += (v[dq.front()]);
    }

    fout << s << '\n';

    return 0;
}