#include <bits/stdc++.h>
using namespace std;

int main() {
    ifstream fin("deque.in");
    ofstream fout("deque.out");
    fin.tie(0);
    std::ios_base::sync_with_stdio(0);
    const int MAX_N = 5000000;
    int v[MAX_N];
    deque<int> dq;
    int n, k;
    long long sumMins = 0;
    fin >> n >> k;
    for (int i = 0; i < n; ++i) {
        fin >> v[i];
        if(!dq.empty() && dq.front() == i - k) {
            dq.pop_front();
        }
        while(!dq.empty() && v[i] <= v[dq.back()]) {
            dq.pop_back();
        }
        dq.push_back(i);
        if (i + 1 >= k) {
            sumMins += v[dq.front()];
        }
    }
    fout << sumMins;
}