#include <fstream>
#include <deque>
#define DMAX 5000004

using namespace std;

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

deque <int> dq;
//dq.empty(); -> returneaza 1 daca e vid
//dq.push_front(val);
//dq.pop_front();
//dq.push_back(val);
//dq.pop_back();
//dq.back();
//dq.front(); -> returneaza valoarea

int n, k;
int a[DMAX];
long long int s;

void citire();
void rez();

int main()
{
    citire();
    rez();
    return 0;
}

void citire()
{
    int i;
    fin>>n>>k;
    for(i=1;i<=n;i++)
        fin>>a[i];
}

void rez()
{
    int i;
    for(i=1;i<=n;i++)
    {
        if(!dq.empty() && dq.front()==i-k)
            dq.pop_front();
        while(!dq.empty() && a[dq.back()]>a[i])
            dq.pop_back();
        dq.push_back(i);
        if(i>=k)
            s+=(long long int)a[dq.front()];
    }
    fout<<s<<'\n';
}