#include <iostream>
#include <fstream>
#include <deque>

using namespace std;


int a[5000001];
int main()
{
    int N,K,i,s=0;
    ifstream f("deque.in");
    ofstream g("deque.out");

    f>>N>>K;
    deque<int> q;///memoram poizitii ale elementelor
    for(i=1;i<=N;i++)f>>a[i];

    for(i=1;i<=N;i++)
    {
        if(!q.empty() && q.front()==i-K)
            q.pop_front();
        while(!q.empty() && a[q.back()]>=a[i])
            q.pop_back();

        q.push_back(i);

        if(i>=K)
            s=s+a[q.front()];
    }

    g<<s;
    return 0;
}