#include <fstream>
#include <deque>

using namespace std;

ifstream f("deque.in");
ofstream g("deque.out");

long long a[5000001],n,k,s;

deque<int>d;

int main()
{
    f>>n>>k;

    for(int i=1;i<=n;++i)
    {
        f>>a[i];
        while(!d.empty() && a[d.back()]>=a[i])
            {
                d.pop_back();
            }
        d.push_back(i);
        if(i-d.front()>=k)
        {
            d.pop_front();
        }
        if(i>=k)
        {
            s+=a[d.front()];
        }
    }
    g<<s;
}