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

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

const int NMAX = 5e6 + 5;
int a[NMAX];

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

    long long ans = 0;
    deque<int> dq;
    for(int i = 1; i <= n; i++)
    {
        while(!dq.empty() && a[i] <= a[dq.back()])
            dq.pop_back();
        dq.push_back(i);

        if(dq.front() == i - k)
            dq.pop_front();

        if(i >= k)
            ans += 1LL * a[dq.front()];
    }
    fout << ans;

    return 0;
}