#include <bits/stdc++.h>

using namespace std;

ifstream fin ("deque.in");
ofstream fout ("deque.out");

int main () {
    int n, k;
    fin >> n >> k;
    int a[n];
    for (int i = 0; i < n; i++) {
        fin >> a[i];
    }
    long long s = 0;
    deque<int>dq;
    for (int i = 0; i < n; i++) {
        while (!dq.empty() && a[dq.back()] >= a[i]) {
            dq.pop_back();
        }
        dq.push_back(i);
        while (!dq.empty() && i - dq.front() + 1 > k) {
            dq.pop_front();
        }
        if (i >= k - 1) {
            s += a[dq.front()];
        }
    }
    fout << s;
}