#include<fstream>
#include<set>
#include<algorithm>
#define _NM 5000010
using namespace std;
int main()
{
    ifstream fin("deque.in");
    ofstream fout("deque.out");
    int nA,k; static int A[_NM];
    fin>>nA>>k;
    multiset<int> ssq;
    long long sum=0;
    for (int i=1;i<=nA;i++)
    {
        fin>>A[i];
        if (i<=k)
        {
            ssq.insert(A[i]);
            if (i==k) sum+=*ssq.begin();
            continue;
        }
        ssq.insert(A[i]);
        ssq.erase(ssq.find(A[i-k]));
        sum+=*ssq.begin();
    }
    fout<<sum;
    return 0;
}