#include <fstream>
#include <deque>
#define DMAX 5000001

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

deque <int> dq;
int n, k, a[DMAX];
long long int S;

void citire();
void rezolvare();

int main()
{
citire();
rezolvare();
fout<<S<<'\n';
fout.close();
return 0;
}

void rezolvare()
{
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+=a[dq.front()];
}
}

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