#include<fstream>
#include<iostream>

using namespace std;

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

int v[5000001],deq[5000001];
int n,k,st,dr;

long long Smin;

int main ()
{
    int i;
    int st = 1, dr = 0;
    f>>n>>k;

    for(i=1;i<=n;i++)
        f>>v[i];

    for(i = 1; i <=n; i++){

        while(dr >= st && v[i] <= v[deq[dr]]) dr--;

        dr++;
        deq[dr] = i;

        if(i >= k){

            Smin+= v[deq[st]];
            if(deq[st] == i - k + 1) st++;
        }
    }

    g<<Smin;

    f.close();
    g.close();
    return 0;
}