#include <fstream>
#include <deque>

using namespace std;
int v[5000005], n, k;
deque <int> q;

ifstream cin("deque.in");
ofstream cout("deque.out");

int main()
{
    cin >> n >> k;
    for (int i = 1; i <= n; i++)
        cin >> v[i];

    long long rez = 0;
    for(int i = 1; i <= n; i++)
    {
        while(!q.empty() && v[q.back()] > v[i])
            q.pop_back();
        q.push_back(i);
        if(q.front() == i - k)
            q.pop_front();
        if(i >= k)
            rez += v[q.front()];
    }

    cout << rez;

    return 0;
}