#include <bits/stdc++.h>

using namespace std;

ifstream fin("deque.in");

ofstream fout("deque.out");

int deq[5000001],v[5000001];

int main()
{
    int n,k,i,rez=0,stanga=0, dreapta=-1;
    fin>>n>>k;
    for(i=0;i<n;i++)
        fin>>v[i];
    for(i=0;i<n;i++)
    {
        while(stanga<=dreapta&&v[i]<=v[deq[dreapta]])
            dreapta--;
        ++dreapta;
        deq[dreapta]=i;
        if(deq[stanga] == i-k)
                stanga++;
        if(i+1 >= k)
            rez += v[deq[stanga]];
    }
    fout<<rez;
    return 0;
}