#include <fstream>
#include <deque>
using namespace std;
deque<int> q;
int v[5000008];
int main()
{
    ifstream fin("deque.in");
    ofstream fout ("deque.out");
    int n,k;
    long long suma=0;
    fin>>n>>k;
    for(int i=1;i<=n;i++)
    {
        fin>>v[i];
    }
    for(int i=1;i<=n;i++)
    {
        while(!q.empty() && v[i]<=v[q.back()]) q.pop_back();
        q.push_back(i);
        if(q.front()<=i-k) q.pop_front();
        if(i>=k) suma+=v[q.front()];
    }
    fout<<suma;
}