#include <iostream>
#include <fstream>
#include <deque>
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
deque <int> q;
int n, k, el, v[5000005];
long long sum;

int main() {
    fin >> n >> k;
    for (int i = 1; i <= n; ++i)
        fin >> v[i];
    for (int j = 1, i = 1; j <= n; ++j) {
        if (j > k) {
            ++i;
            sum += v[q.front()];
            while (q.front() < i)
                q.pop_front();
        }
        while (v[j] < v[q.back()] && !q.empty())
            q.pop_back();
        q.push_back(j);
    }
    sum += v[q.back()];
    fout << sum;
    return 0;
}