#include<fstream>
#include<queue>
#define _NM 5000010
using namespace std;

int A[_NM], nA;
struct greater_A_val
{
    bool operator()(int i1, int i2)
    {
        return A[i1]>A[i2];
    }
};

int main()
{
    ifstream fin("deque.in");
    ofstream fout("deque.out");
    int k; fin>>nA>>k;
    priority_queue<int,vector<int>,greater_A_val > iq;
    long long sum=0;
    for (int i=1;i<=nA;i++)
    {
        fin>>A[i];
        iq.push(i);
        if (i>=k)
        {
            while (!iq.empty()&&iq.top()<=i-k)
                iq.pop();
            sum+=A[iq.top()];
        }
    }
    fout<<sum;
    return 0;
}