#include <fstream>
#include <deque>

using namespace std;

ifstream in("deque.in");
ofstream out("deque.out");
deque <int> dq;

int main()
{
    int long long n,k,st=0,dr=-1,v[1234578],suma=0;
    in>>n>>k;
    for(int i=0; i<n; i++)
    {
        in>>v[i];
        if(st<-dr && dq[st]==i-k)
        {
            st++;
        }
        while(st<=dr && v[i]<=v[dq[dr]])
        {
            dr--;
        }
        dq[++dr]=i;
        if(i>-k-1)
        {
            suma+=v[dq[st]];
        }
    }
    out<<suma;
    return 0;
}