#include <fstream>
#include <deque>
#include <vector>

using namespace std;

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

int n, k;
vector<int> v;
deque<int> index_min;

int main() {
    cin >> n >> k;
    v.resize(n + 1);
    for (int i = 1 ; i <= n ; ++i) {
        cin >> v[i];
    }
    long long ans = 0;
    for (int i = 1 ; i <= n ; ++i) {
        while (!index_min.empty() && v[i] <= v[index_min.back()]) index_min.pop_back();
        index_min.push_back(i);
        if (index_min.front() == i - k) index_min.pop_front();
        if (i >= k) ans += v[index_min.front()];
    }
    cout << ans;
    return 0;
}