#include <fstream>
#include <deque>
using namespace std;
ifstream f("deque.in"); ofstream g("deque.out");
int n,k,v[5000001];
deque <int> coada;
long long s;
int main()
{
    f>>n>>k;
    for(int i=1;i<=n;i++)
    {
        f>>v[i];
        while(!coada.empty() and v[coada.front()]>v[i])
            coada.pop_front();
        coada.push_front(i);
        if(!coada.empty() and i-coada.back()>=k)
            coada.pop_back();
        if(i>=k) s+=v[coada.back()];
    }
    g<<s;
    return 0;
}