#include <bits/stdc++.h>

using namespace std;
long long int v[5000002],n,k,i,s;
deque <int> dechiu;
int main()
{
    ifstream cin("deque.in");
    ofstream cout("deque.out");
    dechiu.push_back(1);
    cin >> n >> k;
    for (i=1;i<=n;i++)
    {
        cin >> v[i];
    }
    for (i=2;i<=n;i++)
    {
        while (!dechiu.empty() && v[i]<=v[dechiu.back()])
        {
            dechiu.pop_back();
        }
        dechiu.push_back(i);
        if (i-dechiu.front()==k)
        {
            dechiu.pop_front();
        }
        if (i>=k)
        {
            s+=v[dechiu.front()];
        }
    }
    cout << s;
}