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

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

deque<int> deq;

int main()
{
    int n, k;
    f >> n >> k;
    int A[n+3];

    for(int i=1; i<=n; i++)
    {
        f >>A[i];
    }
    int s =0;
    for(int i=1; i<=n; i++)
    {
        if(!deq.empty() && deq.front() <= i-k)
            deq.pop_front();

        while(!deq.empty()&& A[deq.back()]>=A[i])
        {
             deq.pop_back();
        }
        deq.push_back(i);
        if (i>=k) s+=A[deq.front()];

    }
    g << s;

    f.close();
    g.close();

    return 0;
}