#include <fstream>
#include <deque>
using namespace std;
ifstream fi("deque.in");
ofstream fo("deque.out");

deque <int> D;
int a[5000001];
int n,k,poz,x,i;
long long sol;

int main()
{
    fi>>n>>k;
    for(i=1;i<=n;i++) fi>>a[i];

while (poz<=n)
{poz++;

while ( ! D.empty() and   D.front() + k <= poz ) D.pop_front();
while ( ! D.empty() and  a[D.front()] > a[poz] ) D.pop_front();

D.push_back(poz);

if (poz>=k) sol+=a[D.front()];
//fo << a[D.front()]<<" ";

}
fo<<sol;


    return 0;
}