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

using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");

int v[5000001];
int main()
{
    deque <int> d;
    long long n,i,k,s=0;
    fin>>n>>k;
    for(i=1;i<=n;i++) fin>>v[i];
    for(i=1;i<=n;i++)
      {
        while(!d.empty() && v[d.back()]>=v[i])
          d.pop_back();
        d.push_back(i);
        if(i-k==d.front())
            d.pop_front();
        if(i>=k)
            s+=v[d.front()];
      }
    fout<<s;
    return 0;
}