#include <fstream>
#include <deque>

using namespace std;
ifstream fin ("deque.in");
ofstream fout ("deque.out");
int n,k,v[5000010],i;
long long s;
deque <int> d;
int main()
{
    fin>>n;
    fin>>k;
    for(i=1;i<=n;i++)
    {
        fin>>v[i];
        if(!d.empty() && d.front()==i-k)
            d.pop_front();
        while(!d.empty() && v[d.back()]>=v[i])
            d.pop_back();
        d.push_back(i);
        if(i>=k) s+=v[d.front()];
    }
    fout<<s;

    return 0;
}