#include <fstream>
#include <queue>

using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
deque<int>d;
int n,k,s,v[5000005],i;
int main()
{
    f>>n>>k;
    for(i=1;i<=n;i++)
        f>>v[i];
    d.push_back(1);
    for(i=2;i<=n;i++)
    {
        while(!d.empty() && v[i]<=v[d.back()])
            d.pop_back();
        d.push_back(i);
        if(i-d.front()>=k)
            d.pop_front();
        if(i>=k)
            s+=v[d.front()];
    }
    g<<s<<'\n';
    return 0;
}