#include <fstream>
#include <deque>

using namespace std;

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

int n,k,v[5000005];
long long sum;
deque<int> d;

int main()
{
    fin>>n>>k;
    for(int i=1;i<=n;i++)fin>>v[i];
    d.push_back(1);
    if(k==1)sum=v[1];
    for(int i=2;i<=n;i++){
        while(!d.empty() && v[i]<=v[d.back()])d.pop_back();
        d.push_back(i);

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

        if(i>=k){
            sum+=v[d.front()];
        }
    }
    fout<<sum;
    return 0;
}