#include <iostream>
#include <fstream>
#include<deque>
using namespace std;
deque <int> d ;
ifstream fin ("deque.in");
ofstream fout ("deque.out");
int v[5000001],n,i,p,u,k,s;
int main()
{
   fin>>n>>k;
   for(i=1;i<=n;i++)
        fin>>v[i];
    for(i=1;i<=n;i++)
    {
        while(!d.empty()&&v[i]<v[d[d.size()-1]])
                d.pop_back();
        d.push_back(i);
        if(d[0]==i-k)
            d.pop_front();
        if(i>=k)
            s+=v[d[0]];
    }
  fout<<s;
    return 0;
}