#include<fstream>
#include<deque>

using namespace std;
int i,n,j,k,cont,ok,maxi,x,y,a[5000100],sum;
deque<int> d;


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

int main()
{
    fin>>n>>k;
    for(i=1;i<=n;i++)
    {
        fin>>a[i];
        while(!d.empty() && a[d.back()]>=a[i]){
            d.pop_back();
        }
        d.push_back(i);
        if(d.front()==i-k)
            d.pop_front();
        if(i>=k)
            sum+=a[d.front()];

    }
    fout<<sum;

}