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

int N,K;
long long Sol;
deque < pair <int,int> > D;

int main()
{
    fin >> N >> K;
     int X;

     for (int i = 1;i <= N;i++)
        {
            fin >> X;
            while(!D.empty() && D.back().first > X)
                D.pop_back();

            D.push_back(make_pair(X,i));

            if (D.front().second + K == i)
                D.pop_front();

            Sol += i < K ? 0 : D.front().first;
        }
     fout << Sol;
    return 0;
}