#include <fstream>
#include <deque>

using namespace std;
int n, k;
long long sol;
deque<int> d;
int v[5000010];

int main() {
    ifstream fin("deque.in");
    ofstream fout("deque.out");
    fin >> n >> k;
    for (int i = 1; i <= n; i++) {
        fin >> v[i];
    }
    d.push_back(1);
    for (int i = 2; i <= n; i++) {
        while (!d.empty() && v[i] <= v[d.back()]) {
            d.pop_back();
        }
        d.push_back(i);
        if (i - d.front() == k) {
            d.pop_front();
        }
        if (i >= k) {
            sol += v[d.front()];
        }
    }
    fout << sol;
    return 0;
}