#include <bits/stdc++.h>

using namespace std;
ifstream f ("deque.in");
ofstream g ("deque.out");
const int NMAX=5e6;
int n, k, v[NMAX+5];
deque <int> coada;
long long sum=0;
int main ()
{
    f >> n >> k;
    for (int i=1;i<=n;i++)
        f >> v[i];
    for (int i=1;i<=n;i++)
    {
        while (!coada.empty() && coada.front()<=i-k)
            coada.pop_front ();
        while (!coada.empty() && v[coada.back()]>=v[i])
            coada.pop_back ();
        coada.push_back (i);
        if (i>=k) sum+=1ll*v[coada.front()];
    }
    g << sum;
    return 0;
}