#include <fstream>
#include <deque>

using namespace std;

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

const int MAX = 5e6 + 1;
int v[MAX], n, k;

deque<int> q;

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

    long long ans = 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){
            ans += v[q.front()];
        }
    }

    cout << ans;

    return 0;
}