#include <fstream>
#include <deque>
#define DIM 5000001

using namespace std;

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

int N, K, A[DIM];
long long Sol;
deque<int> D;

int main()
{
    int i;
    in >> N >> K;
    for (i = 1; i <= N; i++)
    {
        in >> A[i];
    }
    for (i = 1; i <= N; i++)
    {
        while (!D.empty() and A[i] <= A[ D.back() ]) D.pop_back();
        D.push_back(i);
        if (D.front() == i - K) D.pop_front();
        if (i >= K)
        {
            Sol += A[ D.front() ];
        }
    }
    out << Sol;
    return 0;
}