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

using namespace std;

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

int v[5000010];
deque <int> Q;


int main()
{
    int n,k;
    int sum=0;
    in>>n>>k;

    for(int i=0;i<n;i++)
        in>>v[i];

        Q.push_front(0);
    ///Q[0]=v[0];
    for(int i=1;i<n;i++)
    {

            if(Q.front()==i-k)
            {
                  Q.pop_front();
            }

        while(!Q.empty() && v[i]<v[Q.back()])
        {
             Q.pop_back();

        }
            Q.push_back(i);

        if(i>=k-1)
            sum+=v[Q.front()];


    }
    out<<sum;

    return 0;
}