#include <iostream>
#include <fstream>
#include <deque>

using namespace std;

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

int v[5000005];

int main()
{
    int n, k, sum=0;
    fin>>n>>k;
    for(int i=1;i<=n;i++)
    {
        fin>>v[i];
    }

    deque <int> dq;

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

    fout<<sum;

    return 0;
}