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

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

int n, k, a[5000007];
deque <int> q;
long long minim;

int main()
{
    int i;

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

    for (i=1; i<=k; i++)
    {
        while (!q.empty() && a[i]<=a[q.back()])
            q.pop_back();

        /// scot din q toate elem mai mari
        /// sau egale cu a[i]

        q.push_back(i);
    }
    minim+=a[q.front()];

    /// restul elem

    for (i=k+1; i<=n; i++)
    {
        while (!q.empty() && a[i]<=a[q.back()])
            q.pop_back();
        q.push_back(i);

        ///verificam daca am invechit un element

        if (i-q.front()>=k)
            q.pop_front();
        minim+=a[q.front()];
    }
    fout << minim << "\n";

    fin.close();
    fout.close();
    return 0;
}