#include <bits/stdc++.h>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
int v[5000009];
deque <int> dq;
int s=0;
signed main ()
{
    int n, k;
    f >> n >> k;
    long long ans=0;
    for (int i=1; i<=n; i++)
        f >> v[i];
    for (int i=1; i<=k; i++)
    {
        while (!dq.empty() && v[i]<v[dq.front()])
            dq.pop_front();
        dq.push_front(i);
    }
    ans+=v[dq.back()];
    for (int i=k+1; i<=n; i++)
    {
        if (i-dq.back()>=k)
            dq.pop_back();
        while (!dq.empty() && v[i]<v[dq.front()])
            dq.pop_front();
        dq.push_front(i);
        ans+=v[dq.back()];
    }
    g << ans;
}