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

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

int main()
{
    int k,n,c=0,i,x;
    deque<int> q,v;
    f>>n>>k;
    for(i=1;i<=n;i++)
    {
        f>>x;
        while(x<q.back() && q.size()!=0)
        {
            q.pop_back();
            v.pop_back();
        }
        q.push_back(x);
        v.push_back(i);
        if(i-v.front()>=k)
        {
            q.pop_front();
            v.pop_front();
        }
        c+=q.front();
    }
    g<<c;
    g.close();
    f.close();
    return 0;
}