#include <fstream>
#include <deque>


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