#include <fstream>
#include <deque>
#define N_MAX 5000003
using namespace std;

int n, k;
int val[N_MAX];
deque <int> A;
long long s;

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

int main()
{
    fin>>n>>k;
    int i;
    for(i=1;i<=n;++i)
       fin>>val[i];
    s=0;
    for (i=1;i<=n;++i)
    {
        while (!A.empty() && val[i]<val[A.back()])  A.pop_back();

        A.push_back(i);

        if (A.front()==i-k)
            A.pop_front();

        if (i>=k)
           s+=val[A.front()];
    }

    fout<<s;

    return 0;
}