#include <iostream>
#include <deque>
#include <fstream>
using namespace std;

int main()
{
    ifstream cin("deque.in");
    ofstream cout("deque.out");
    long long s=0;
    deque <int> q;
    int n,k;
    cin>>n>>k;
    int v[n];
    for(int i=1;i<=n;i++)
        cin>>v[i];

    q.push_back(1);
    for(int i=2;i<=n;i++)
    {
        while(!q.empty() && v[i]<=v[q.back()])
            q.pop_back();


        q.push_back(i);
        if(i-q.front()==k)
            q.pop_front();
        if(i>=k)
            {
                s+=v[q.front()];
                }
    }
    cout<<s;
    return 0;
}