#include <fstream>
#include <deque>
using namespace std;
ifstream  fin("deque.in");
ofstream fout("deque.out");
int N,K,i,j,A[5000002];
long long s;
deque <int> d;
int main()
{
    fin>>N>>K;

    for(i=1; i<=N; i++)
    {
        fin>>A[i];
    }

    s=0;


    for(i=1; i<=N; i++)
    {
        while(!d.empty() && A[i]<=A[d.back()])
        {
           d.pop_back();
        }

        d.push_back(i);

        if(d.front()==i-K)
        {
            d.pop_front();
        }

        if(i>=K)
        {
            s+=A[d.front()];
        }
    }

    fout<< s;

    return 0;
}