#include <fstream>
#include <deque>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");

deque<int>c;
int n,k,i,s,v[5000001];
int main()
{
    f>>n>>k;
    for(i=1;i<=n;i++)
        f>>v[i];
    c.push_back(1);
    for(i=2;i<=n;i++)
    {


        while(v[c.back()]>v[i]&&c.size()!=0)
        {
            if(c.size()==0)break;
               else c.pop_back();
        }
    c.push_back(i);
    if(c.back()-c.front()>=k){c.pop_front();}
    if(i>=k)s=s+v[c.front()];
    }
    g<<s;
    return 0;
}