#include <bits/stdc++.h>
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
const int nmax = 5e6 + 1 ;
int v[nmax];
int main() {
    ios::sync_with_stdio(false);
    fin.tie(nullptr);
    int n, k;
    fin>>n>>k;
    deque<int>deq;
    long long sum = 0;
    for (int i=1 ;i<=n;i++) {
        fin>>v[i];
        while (!deq.empty() && deq.back() >= v[i]) {
            deq.pop_back();
        }
        deq.push_back(i);
        if (i >= k ) {
            if (deq.front() <= i - k) {
                deq.pop_front();
                sum += v[deq.front()];
            }

        }

    }
   fout<<sum;
}