#include <fstream>
#include <deque>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
deque<int>d;
long long a[5000001],k,i,s=0,n,l=0;
int main()
{
    f>>n>>k;
    for(i=1;i<=n;i++) f>>a[i];
    d.push_back(1);
    for(i=2;i<=n;i++)
    {
        while(!d.empty()&&a[d.back()]>a[i])
        {
            if(d.size()==0)break;
               else d.pop_back();
        }
        d.push_back(i);
        if(d.back()-d.front()>=k) d.pop_front();
       if(i>=k) s=s+a[d.front()];

    }
    g<<s;
    return 0;
}